Interplay between reference picture resampling and video coding tools

ABSTRACT

An example method of video processing includes determining, for a conversion between a current block of a current picture of a video and a bitstream of the video, whether to disable a coding tool for the current block; and performing the conversion based on the determining, wherein the coding tool is disabled when a dimension of a reference picture of one or more reference pictures of the current block is different from a dimension of the current picture, or a dimension of a scaling window in a reference picture of one or more reference pictures of the current block is different from a dimension of a scaling window in the current picture.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 17/719,708, filed on Apr. 13, 2022, which is acontinuation of International Application No. PCT/CN2020/120554, filedon Oct. 13, 2020, which claims the priority to and benefits of U.S.Provisional Patent Application No. 62/914,544, filed on Oct. 13, 2019.For all purposes under the law, the entire disclosure of theaforementioned application is incorporated by reference as part of thedisclosure of this application.

TECHNICAL FIELD

This patent document relates to video coding techniques, devices andsystems.

BACKGROUND

Currently, efforts are underway to improve the performance of currentvideo codec technologies to provide better compression ratios or providevideo coding and decoding schemes that allow for lower complexity orparallelized implementations. Industry experts have recently proposedseveral new video coding tools and tests are currently underway fordetermining their effectivity.

SUMMARY

Devices, systems and methods related to digital video coding, andspecifically, to management of motion vectors are described. Thedescribed methods may be applied to existing video coding standards(e.g., High Efficiency Video Coding (HEVC) or Versatile Video Coding)and future video coding standards or video codecs.

In one representative aspect, the disclosed technology may be used toprovide a method for video processing. This method includes performing aconversion between a current video block and a coded representation ofthe current video block, wherein, during the conversion, if a resolutionand/or a size of a reference picture is different from a resolutionand/or a size of the current video block, a same interpolation filter isapplied to a group of adjacent or non-adjacent samples predicted usingthe current video block.

In another representative aspect, the disclosed technology may be usedto provide another method for video processing. This method includesperforming a conversion between a current video block and a codedrepresentation of the current video block, wherein, during theconversion, if a resolution and/or a size of a reference picture isdifferent from a resolution and/or a size of the current video block,wherein blocks predicted using the current video block are only allowedto use integer-valued motion information related to the current block.

In another representative aspect, the disclosed technology may be usedto provide another method for video processing. This method includesperforming a conversion between a current video block and a codedrepresentation of the current video block, wherein, during theconversion, if a resolution and/or a size of a reference picture isdifferent from a resolution and/or a size of the current video block, aninterpolation filter is applied to derive blocks predicted using thecurrent video block, and wherein the interpolation filter is selectedbased on a rule.

In another representative aspect, the disclosed technology may be usedto provide another method for video processing. This method includesperforming a conversion between a current video block and a codedrepresentation of the current video block, wherein, during theconversion, if a resolution and/or a size of a reference picture isdifferent from a resolution and/or a size of the current video block,selectively applying a deblocking filter, wherein a strength of thedeblocking filter set in accordance with a rule related to theresolution and/or the size of the reference picture relative to theresolution and/or the size of the current video block.

In another representative aspect, the disclosed technology may be usedto provide another method for video processing. This method includesperforming a conversion between a current video block and a codedrepresentation of the current video block, wherein, during theconversion, a reference picture of the current video block is resampledin accordance with a rule based on dimensions of the current videoblock.

In another representative aspect, the disclosed technology may be usedto provide another method for video processing. This method includesperforming a conversion between a current video block and a codedrepresentation of the current video block, wherein, during theconversion, a use of a coding tool on the current video block isselectively enabled or disabled depending on a resolution/size of areference picture of the current video block relative to aresolution/size of the current video block.

In another representative aspect, the disclosed technology may be usedto provide another method for video processing. This method includesperforming a conversion between multiple video blocks and codedrepresentations of the multiple video blocks, wherein, during theconversion, a first conformance window is defined for a first videoblock and a second conformance window for a second video block, andwherein a ratio of a width and/or a height of the first conformancewindow to the second conformance window is in accordance with a rulebased at least on a conformance bitstream.

In another representative aspect, the disclosed technology may be usedto provide another method for video processing. This method includesperforming a conversion between multiple video blocks and codedrepresentations of the multiple video blocks, wherein, during theconversion, a first conformance window is defined for a first videoblock and a second conformance window for a second video block, andwherein a ratio of a width and/or a height of the first conformancewindow to the second conformance window is in accordance with a rulebased at least on a conformance bitstream.

Further, in a representative aspect, an apparatus in a video systemcomprising a processor and a non-transitory memory with instructionsthereon is disclosed. The instructions upon execution by the processor,cause the processor to implement any one or more of the disclosedmethods.

In one representative aspect, a video decoding apparatus comprising aprocessor configured to implement a method recited herein is disclosed.

In one representative aspect, a video encoding apparatus comprising aprocessor configured to implement a method recited herein is disclosed.

Also, a computer program product stored on a non-transitory computerreadable media, the computer program product including program code forcarrying out any one or more of the disclosed methods is disclosed.

The above and other aspects and features of the disclosed technology aredescribed in greater detail in the drawings, the description and theclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of sub-block motion vector (VSB) and motionvector difference.

FIG. 2 shows an example of a 16×16 video block divided into 16 4×4regions.

FIG. 3A shows an example of a specific position in a sample.

FIG. 3B shows another example of a specific position in a sample.

FIG. 3C shows yet another example of a specific position in a sample.

FIG. 4A shows an example of positions of the current sample and itsreference sample.

FIG. 4B shows another example of positions of the current sample and itsreference sample.

FIG. 5 is a block diagram of an example of a hardware platform forimplementing a visual media decoding or a visual media encodingtechnique described in the present document.

FIG. 6 shows a flowchart of an example method for video coding.

FIG. 7 shows an example of decoder side motion vector refinement.

FIG. 8 shows an example of flow of cascading DMVR and BDOF processes inVTM5.0. The DMVR SAD operations and BDOF SAD operations are differentand not shared.

FIG. 9 is a block diagram of an example video processing system in whichdisclosed techniques may be implemented.

FIG. 10 is a block diagram that illustrates an example video codingsystem.

FIG. 11 is a block diagram that illustrates an encoder in accordancewith some embodiments of the present disclosure.

FIG. 12 is a block diagram that illustrates a decoder in accordance withsome embodiments of the present disclosure.

FIG. 13 is a flowchart representation of a method for video processingin accordance with the present technology.

FIG. 14 is a flowchart representation of another method for videoprocessing in accordance with the present technology.

FIG. 15 is a flowchart representation of yet another method for videoprocessing in accordance with the present technology.

DETAILED DESCRIPTION 1. Video Coding in HEVC/H.265

Video coding standards have evolved primarily through the development ofthe well-known ITU-T and ISO/IEC standards. The ITU-T produced H.261 andH.263, ISO/IEC produced MPEG-1 and MPEG-4 Visual, and the twoorganizations jointly produced the H.262/MPEG-2 Video and H.264/MPEG-4Advanced Video Coding (AVC) and H.265/HEVC standards. Since H.262, thevideo coding standards are based on the hybrid video coding structurewherein temporal prediction plus transform coding are utilized. Toexplore the future video coding technologies beyond HEVC, Joint VideoExploration Team (JVET) was founded by VCEG and MPEG jointly in 2015.Since then, many new methods have been adopted by JVET and put into thereference software named Joint Exploration Model (JEM). In April 2018,the Joint Video Expert Team (JVET) between VCEG (Q6/16) and ISO/IEC JTC1SC29/WG11 (MPEG) was created to work on the VVC standard targeting at50% bitrate reduction compared to HEVC.

2. Overview 2.1. Adaptive Resolution Change (ARC)

AVC and HEVC does not have the ability to change resolution withouthaving to introduce an IDR or intra random access point (TRAP) picture;such ability can be referred to as adaptive resolution change (ARC).There are use cases or application scenarios that would benefit from anARC feature, including the following:

-   -   Rate adaption in video telephony and conferencing: For adapting        the coded video to the changing network conditions, when the        network condition gets worse so that available bandwidth becomes        lower, the encoder may adapt to it by encoding smaller        resolution pictures. Currently, changing picture resolution can        be done only after an TRAP picture; this has several issues. An        TRAP picture at reasonable quality will be much larger than an        inter-coded picture and will be correspondingly more complex to        decode: this costs time and resource. This is a problem if the        resolution change is requested by the decoder for loading        reasons. It can also break low-latency buffer conditions,        forcing an audio re-sync, and the end-to-end delay of the stream        will increase, at least temporarily. This can give a poor user        experience.    -   Active speaker changes in multi-party video conferencing: For        multi-party video conferencing, it is common that the active        speaker is shown in bigger video size than the video for the        rest of conference participants. When the active speaker        changes, picture resolution for each participant may also need        to be adjusted. The need to have ARC feature becomes more        important when such change in active speaker happens frequently.    -   Fast start in streaming: For streaming application, it is common        that the application would buffer up to certain length of        decoded picture before start displaying. Starting the bitstream        with smaller resolution would allow the application to have        enough pictures in the buffer to start displaying faster.

Adaptive stream switching in streaming: The Dynamic Adaptive Streamingover HTTP (DASH) specification includes a feature named@mediaStreamStructureId. This enables switching between differentrepresentations at open-GOP random access points with non-decodableleading pictures, e.g., CRA pictures with associated RASL pictures inHEVC. When two different representations of the same video havedifferent bitrates but the same spatial resolution while they have thesame value of @mediaStreamStructureId, switching between the tworepresentations at a CRA picture with associated RASL pictures can beperformed, and the RASL pictures associated with the switching-at CRApictures can be decoded with acceptable quality hence enabling seamlessswitching. With ARC, the @mediaStreamStructureId feature would also beusable for switching between DASH representations with different spatialresolutions.

ARC is also known as Dynamic resolution conversion.

ARC may also be regarded as a special case of Reference PictureResampling (RPR) such as H.263 Annex P.

2.2. Reference Picture Resampling in H.263 Annex P

This mode describes an algorithm to warp the reference picture prior toits use for prediction. It can be useful for resampling a referencepicture having a different source format than the picture beingpredicted. It can also be used for global motion estimation, orestimation of rotating motion, by warping the shape, size, and locationof the reference picture. The syntax includes warping parameters to beused as well as a resampling algorithm. The simplest level of operationfor the reference picture resampling mode is an implicit factor of 4resampling as only an FIR filter needs to be applied for the upsamplingand downsampling processes. In this case, no additional signalingoverhead is required as its use is understood when the size of a newpicture (indicated in the picture header) is different from that of theprevious picture.

2.3. Conformance Window in VVC

Conformance window in VVC defines a rectangle. Samples inside theconformance window belongs to the image of interest. Samples outside theconformance window may be discarded when output.

When conformance window is applied, the scaling ration in RPR is derivedbased on conformance windows.

Picture Parameter Set RBSP Syntax

pic_parameter_set_rbsp( ) { Descriptor  pps_pic_parameter set_id ue(v) pps_seq_parameter_set_id ue(v)  pic_width_in luma samples ue(v) pic_height_in_luma_samples ue(v)

 

 

 

 

}pic_width_in_luma_samples specifies the width of each decoded picturereferring to the PPS in units of luma samples. pic_width_in_luma_samplesshall not be equal to 0, shall be an integer multiple of Max(8,MinCbSizeY), and shall be less than or equal topic_width_max_in_luma_samples.When subpics_present_flag is equal to 1, the value ofpic_width_in_luma_samples shall be equal topic_width_max_in_luma_samplespic_height_in_luma_samples specifies the height of each decoded picturereferring to the PPS in units of luma samples.pic_height_in_luma_samples shall not be equal to 0 and shall be aninteger multiple of Max(8, MinCbSizeY), and shall be less than or equalto pic_height_max_in_luma_samples.When subpics_present_flag is equal to 1, the value ofpic_height_in_luma_samples shall be equal topic_height_max_in_luma_samples.Let refPicWidthInLumaSamples and refPicHeightInLumaSamples be thepic_width_in_luma_samples and pic_height_in_luma_samples, respectively,of a reference picture of a current picture referring to this PPS. Is arequirement of bitstream conformance that all of the followingconditions are satisfied:

-   -   

    -   

    -   

    -           conformance_window_flag equal to 1 indicates that the        conformance cropping window offset parameters follow next in the        SPS. conformance_window_flag equal to 0 indicates that the        conformance cropping window offset parameters are not present.        conf_win_left_offset, conf_win_right_offset,        conf_win_top_offset, and conf_win_bottom_offset specify the        samples of the pictures in the CVS that are output from the        decoding process, in terms of a rectangular region specified in        picture coordinates for output. When conformance_window_flag is        equal to 0, the values of conf_win_left_offset,        conf_win_right_offset, conf_win_top_offset, and        conf_win_bottom_offset are inferred to be equal to 0.        The conformance cropping window contains the luma samples with        horizontal picture coordinates from        SubWidthC*conf_win_left_offset to        pic_width_in_luma_samples−(SubWidthC*conf_win_right_offset+1)        and vertical picture coordinates from        SubHeightC*conf_win_top_offset to        pic_height_in_luma_samples−(SubHeightC*conf_win_bottom_offset+1),        inclusive.        The value of        SubWidthC*(conf_win_left_offset+conf_win_right_offset) shall be        less than pic_width_in_luma_samples, and the value of        SubHeightC*(conf_win_top_offset+conf_win_bottom_offset) shall be        less than pic_height_in_luma_samples.        The variables PicOutputWidthL and PicOutputHeightL are derived        as follows:

PicOutputWidthL=pic_width_in_luma_samples−SubWidthC*(conf_win_right_offset+conf_win_left_offset)  (7-43)

PicOutputHeightL=pic_height_in_pic_size_units−SubHeightC*(conf_win_bottom_offset+conf_win_top_offset)  (7-44)

When ChromaArrayType is not equal to 0, the corresponding specifiedsamples of the two chroma arrays are the samples having picturecoordinates (x/SubWidthC, y/SubHeightC), where (x, y) are the picturecoordinates of the specified luma samples.

Let ppsA and ppsB be any two PPSs referring to the same SPS. It is arequirement of bitstream conformance that, when ppsA and ppsB have thesame the values of pic_width_in_luma_samples andpic_height_in_luma_samples, respectively, ppsA and ppsB shall have thesame values of conf_win_left_offset, conf_win_right_offset,conf_win_top_offset, and conf_win_bottom_offset, respectively.

2.4. Reference Picture Resampling (RPR)

In some embodiments, ARC is also known as Reference Picture Resampling(RPR). With RPR, TMVP is disabled if the collocated picture has adifferent resolution to the current picture. Besides, Bi-DirectionalOptical Flow (BDOF) and Decoder-side Motion Vector Refinement (DMVR) aredisabled when the reference picture has a different resolution to thecurrent picture.

To handle the normal MC when the reference picture has a differentresolution than the current picture, the interpolation section isdefined as below:

8.5.6.3 Fractional Sample Interpolation Process 8.5.6.3.1 General

Inputs to this process are:

-   -   a luma location (xSb, ySb) specifying the top-left sample of the        current coding subblock relative to the top-left luma sample of        the current picture,    -   a variable sbWidth specifying the width of the current coding        subblock,    -   a variable sbHeight specifying the height of the current coding        subblock,    -   a motion vector offset mvOffset,    -   a refined motion vector refMvLX,    -   the selected reference picture sample array refPicLX,    -   the half sample interpolation filter index hpelIfIdx,    -   the bi-directional optical flow flag bdofFlag,    -   a variable cIdx specifying the colour component index of the        current block.        Outputs of this process are:    -   an (sbWidth+brdExtSize)×(sbHeight+brdExtSize) array        predSamplesLX of prediction sample values. The prediction block        border extension size brdExtSize is derived as follows:

brdExtSize=(bdofFlagν(inter_affine_flag[xSb][ySb]&&sps_affine_prof_enabled_flag))?2:0  (8-752)

The variable fRefWidth is set equal to the PicOutputWidthL of thereference picture in luma samples.The variable fRefHeight is set equal to PicOutputHeightL of thereference picture in luma samples.The motion vector mvLX is set equal to (refMvLX−mvOffset).

-   -   If cIdx is equal to 0, the following applies:        -   The scaling factors and their fixed-point representations            are defined as

hori_scale_fp=((fRefWidth<<14)+(PicOutputWidthL>>1))/PicOutputWidthL  (8-753)

vert_scale_fp=((fRefHeight<<14)+(PicOutputHeightL>>1))/PicOutputHeightL  (8-754)

-   -   Let (xIntL, yIntL) be a luma location given in full-sample units        and (xFracL, yFracL) be an offset given in 1/16-sample units.        These variables are used only in this clause for specifying        fractional-sample locations inside the reference sample arrays        refPicLX.        -   The top-left coordinate of the bounding block for reference            sample padding (xSbIntL, ySbIntL) is set equal to            (xSb+(mvLX[0]>>4), ySb+(mvLX[1]>>4)).        -   For each luma sample location (x_(L)=0 . . .            sbWidth−1+brdExtSize, y_(L)=0 . . . sbHeight−1+brdExtSize)            inside the prediction luma sample array predSamplesLX, the            corresponding prediction luma sample value            predSamplesLX[x_(L)][y_(L)] is derived as follows:            -   Let (refxSb_(L), refySb_(L)) and (refx_(L), refy_(L)) be                luma locations pointed to by a motion vector                (refMvLX[0], refMvLX[1]) given in 1/16-sample units. The                variables refxSb_(L), refx_(L), refySb_(L), and                refy_(L), are derived as follows:

refxSb_(L)=((xSb<<4)+refMvLX[0])*hori_scale_fp  (8-755)

refx_(L)=((Sign(refxSb)*((Abs(refxSb)+128)>>8)+x_(L)*((hori_scale_fp+8)>>4))+32)>>6  (8-756)

refySb_(L)=((ySb<<4)+refMvLX[1])*vert_scale_fp  (8-757)

refy_(L)=((Sign(refySb)*((Abs(refySb)+128)>>8)+y_(L)*((vert_scale_fp+8)>>4))+32)>>6  (8-758)

-   -   -   -   The variables xInt_(L), yInt_(L), xFrac_(L) and                yFrac_(L) are derived as follows:

xInt_(L)=refx_(L)>>4  (8-759)

yInt_(L)=refy_(L)>>4  (8-760)

xFrac_(L)=refx_(L)&15  (8-761)

yFrac_(L)=refy_(L)&15  (8-762)

-   -   If bdofFlag is equal to TRUE or (sps_affine_prof_enabled_flag is        equal to TRUE and inter_affine_flag[xSb][ySb] is equal to TRUE),        and one or more of the following conditions are true, the        prediction luma sample value predSamplesLX[x_(L)][y_(L)] is        derived by invoking the luma integer sample fetching process as        specified in clause 8.5.6.3.3 with (xInt_(L)+(xFrac_(L)>>3)−1),        yInt_(L)+(yFrac_(L)>>3)−1) and refPicLX as inputs.        -   -   x_(L) is equal to 0.            -   x_(L) is equal to sbWidth+1.            -   y_(L) is equal to 0.            -   y_(L) is equal to sbHeight+1.

        -   Otherwise, the prediction luma sample value            predSamplesLX[x_(L)][y_(L)] is derived by invoking the luma            sample 8-tap interpolation filtering process as specified in            clause 8.5.6.3.2 with (xInt_(L)−(brdExtSize>0?1:0),            yInt_(L)−(brdExtSize>0?1:0)), (xFracL, yFracL), (xSbInt_(L),            ySbInt_(L)), refPicLX, hpelIfIdx, sbWidth, sbHeight and            (xSb, ySb) as inputs.    -   Otherwise (cIdx is not equal to 0), the following applies:        -   Let (xIntC, yIntC) be a chroma location given in full-sample            units and (xFracC, yFracC) be an offset given in 1/32 sample            units. These variables are used only in this clause for            specifying general fractional-sample locations inside the            reference sample arrays refPicLX.        -   The top-left coordinate of the bounding block for reference            sample padding (xSbIntC, ySbIntC) is set equal to            ((xSb/SubWidthC)+(mvLX[0]>>5),            (ySb/SubHeightC)+(mvLX[1]>>5)).        -   For each chroma sample location (xC=0 . . . sbWidth−1, yC=0            . . . sbHeight−1) inside the prediction chroma sample arrays            predSamplesLX, the corresponding prediction chroma sample            value predSamplesLX[xC][yC] is derived as follows:            -   Let (refxSb_(C), refySb_(C)) and (refx_(C), refy_(C)) be                chroma locations pointed to by a motion vector (mvLX[0],                mvLX[1]) given in 1/32-sample units. The variables                refxSb_(C), refySb_(C), refx_(C) and refy_(C) are                derived as follows:

refxSb_(C)=((xSb/SubWidthC<<5)+mvLX[0])*hori_scale_fp  (8-763)

refx_(C)=((Sign(refxSb_(C))*((Abs(refxSb_(C))+256)>>9)+xC*((hori_scale_fp+8)>>4))+16)>>5  (8-764)

refySb_(C)=((ySb/SubHeightC<<5)+mvLX[1])*vert_scale_fp  (8-765)

refy_(C)=((Sign(refySb_(C))*((Abs(refySb_(C))+256)>>9)+yC*((vert_scale_fp+8)>>4))+16)>>5  (8-766)

-   -   -   -   The variables xInt_(C), yInt_(C), xFrac_(C) and                yFrac_(C) are derived as follows:

xInt_(C)=refx_(C)>>5  (8-767)

yInt_(C)=refy_(C)>>5  (8-768)

xFrac_(C)=refy_(C)&31  (8-769)

yFrac_(C)=refy_(C)&31  (8-770)

-   -   The prediction sample value predSamplesLX[xC][yC] is derived by        invoking the process specified in clause 8.5.6.3.4 with (xIntC,        yIntC), (xFracC, yFracC), (xSbIntC, ySbIntC), sbWidth, sbHeight        and refPicLX as inputs.        8.5.6.3.2 Luma sample interpolation filtering process        Inputs to this process are:    -   a luma location in full-sample units (xInt_(L), yInt_(L)),    -   a luma location in fractional-sample units (xFrac_(L),        yFrac_(L)),    -   a luma location in full-sample units (xSbInt_(L), ySbInt_(L))        specifying the top-left sample of the bounding block for        reference sample padding relative to the top-left luma sample of        the reference picture,    -   the luma reference sample array refPicLX_(L),    -   the half sample interpolation filter index hpelIfIdx,    -   a variable sbWidth specifying the width of the current subblock,    -   a variable sbHeight specifying the height of the current        subblock,    -   a luma location (xSb, ySb) specifying the top-left sample of the        current subblock relative to the top-left luma sample of the        current picture,        Output of this process is a predicted luma sample value        predSampleLX_(L)        The variables shift1, shift2 and shift3 are derived as follows:    -   The variable shift1 is set equal to Min(4, BitDepth_(Y)−8), the        variable shift2 is set equal to 6 and the variable shift3 is set        equal to Max(2, 14−BitDepth_(Y)).    -   The variable picW is set equal to pic_width_in_luma_samples and        the variable picH is set equal to pic_height_in_luma_samples.        The luma interpolation filter coefficients f_(L)[p] for each        1/16 fractional sample position p equal to xFrac_(L) or        yFrac_(L) are derived as follows:    -   If MotionModeIIdc[xSb][ySb] is greater than 0, and sbWidth and        sbHeight are both equal to 4, the luma interpolation filter        coefficients f_(L)[p] are specified in Table 2.    -   Otherwise, the luma interpolation filter coefficients f_(L)[p]        are specified in Table 1 depending on hpelIfIdx.        The luma locations in full-sample units (xInt_(i), yInt_(i)) are        derived as follows for i=0 . . . 7:    -   If subpic_treated_as_pic_flag[SubPicIdx] is equal to 1, the        following applies:

xInt_(i)=Clip3(SubPicLeftBoundaryPos,SubPicRightBoundaryPos,xInt_(L)+i−3)  (8-771)

y Int_(i)=Clip3(SubPicTopBoundaryPos,SubPicBotBoundaryPos,y Int_(L)+i−3)  (8-772)

-   -   Otherwise (subpic_treated_as_pic_flag[SubPicIdx] is equal to 0),        the following applies:

xInt_(i)=Clip3(0,picW−1,sps_ref_wraparound_enabled_flag?ClipH((sps_ref_wraparound_offset_minus1+1)*MinCbSizeY,picW,xInt_(L)+i−3): xInt_(L) +i−3)  (8-773)

yInt_(i)=Clip3(0,picH−1,yInt_(L) +i−3)  (8-774)

The luma locations in full-sample units are further modified as followsfor i=0 . . . 7:

xInt_(i)=Clip3(xSbInt_(L)−3,xSbInt_(L)+sbWidth+4,xInt_(i))  (8-775)

yInt_(i)=Clip3(ySbInt_(L)−3,ySbInt_(L)+sbHeight+4,yInt_(i))  (8-776)

The predicted luma sample value predSampleLX_(L) is derived as follows:

-   -   If both xFrac_(L) and yFrac_(L) are equal to 0, the value of        predSampleLX_(L) is derived as follows:

predSampleLX_(L)=refPicLX_(L) [xInt₃ ][yInt₃]<<shift3  (8-777)

-   -   Otherwise, if xFrac_(L) is not equal to 0 and yFrac_(L) is equal        to 0, the value of predSampleLX_(L) is derived as follows:

predSampleLX_(L)=(Σ_(i=0) ⁷ f _(L)[xFrac_(L) ][i]*refPicLX_(L) [xInt_(i)][yInt₃])>>shift1  (8-778)

-   -   Otherwise, if xFrac_(L) is equal to 0 and yFrac_(L) is not equal        to 0, the value of predSampleLX_(L) is derived as follows:

predSampleLX_(L)=(Σ_(i=0) ⁷ f _(L)[yFrac_(L) ][i]*refPicLX_(L) [xInt₃][yInt_(i)])>>shift1  (8-779)

-   -   Otherwise, if xFrac_(L) is not equal to 0 and yFrac_(L) is not        equal to 0, the value of predSampleLX_(L) is derived as follows:        -   The sample array temp[n] with n=0 . . . 7, is derived as            follows:

temp[n]=(Σ_(i=0) ⁷ f _(L)[xFrac_(L) ][i]*refPicLX_(L) [xInt_(i)][yInt_(i)])>>shift1  (8-780)

-   -   The predicted luma sample value predSampleLX_(L) is derived as        follows:

predSampleLX_(L)=(Σ_(i=0) ⁷ f _(L)[yFrac_(L)][i]*temp[i])>>shift2  (8-781)

TABLE 8-11 Specification of the luma interpolation filter coefficientsf_(L)[p] for each 1/16 fractional sample position p. Fractional sampleinterpolation filter coefficients position p f_(L)[p][0] f_(L)[p][1]f_(L)[p][2] f_(L)[p][3] f_(L)[p][4] f_(L)[p][5] f_(L)[p][6] f_(L)[p][7]1 0 1 −3 63 4 −2 1 0 2 −1 2 −5 62 8 −3 1 0 3 −1 3 −8 60 13 −4 1 0 4 −1 4−10 58 17 −5 1 0 5 −1 4 −11 52 26 −8 3 −1 6 −1 3 −9 47 31 −10 4 −1 7 −14 −11 45 34 −10 4 −1 8 (hpelIfIdx == 0) −1 4 −11 40 40 −11 4 −1 8(hpelIfIdx == 1) 0 3 9 20 20 9 3 0 9 −1 4 −10 34 45 −11 4 −1 10 −1 4 −1031 47 −9 3 −1 11 −1 3 −8 26 52 −11 4 −1 12 0 1 −5 17 58 −10 4 −1 13 0 1−4 13 60 −8 3 −1 14 0 1 −3 8 62 −5 2 −1 15 0 1 −2 4 63 −3 1 0

TABLE 8-12 Specification of the luma interpolation filter coefficientsf_(L)[p] for each 1/16 fractional sample position p for affine motionmode. Fractional sample interpolation filter coefficients position pf_(L)[p][0] f_(L)[p][1] f_(L)[p][2] f_(L)[p][3] f_(L)[p][4] f_(L)[p][5]f_(L)[p][6] f_(L)[p][7] 1 0 1 −3 63 4 −2 1 0 2 0 1 −5 62 8 −3 1 0 3 0 2−8 60 13 −4 1 0 4 0 3 −10 58 17 −5 1 0 5 0 3 −11 52 26 −8 2 0 6 0 2 −947 31 −10 3 0 7 0 3 −11 45 34 −10 3 0 8 0 3 −11 40 40 −11 3 0 9 0 3 −1034 45 −11 3 0 10 0 3 −10 31 47 −9 2 0 11 0 2 −8 26 52 −11 3 0 12 0 1 −517 58 −10 3 0 13 0 1 −4 13 60 −8 2 0 14 0 1 −3 8 62 −5 1 0 15 0 1 −2 463 −3 1 0

8.5.6.3.3 Luma Integer Sample Fetching Process

Inputs to this process are:

-   -   a luma location in full-sample units (xInt_(L), yInt_(L)),    -   the luma reference sample array refPicLX_(L),        Output of this process is a predicted luma sample value        predSampleLX_(L)        The variable shift is set equal to Max(2, 14−BitDepth_(Y)).        The variable picW is set equal to pic_width_in_luma_samples and        the variable picH is set equal to pic_height_in_luma_samples.        The luma locations in full-sample units (xInt, yInt) are derived        as follows:

xInt=Clip3(0,picW−1,sps_ref_wraparound_enabled_flag?ClipH((sps_ref_wraparound_offset_minus1+1)*MinCbSizeY,picW,xInt_(L)):xInt_(L))  (8-782)

yInt=Clip3(0,picH−1,yInt_(L))  (8-783)

The predicted luma sample value predSampleLX_(L) is derived as follows:

predSampleLX_(L)=refPicLX_(L)[xInt][yInt]<<shift3   (8-784)

8.5.6.3.4 Chroma Sample Interpolation Process

Inputs to this process are:

-   -   a chroma location in full-sample units (xInt_(C), yInt_(C)),    -   a chroma location in 1/32 fractional-sample units (xFrac_(C),        yFrac_(C)),    -   a chroma location in full-sample units (xSbInt_(C), ySbInt_(C))        specifying the top-left sample of the bounding block for        reference sample padding relative to the top-left chroma sample        of the reference picture,    -   a variable sbWidth specifying the width of the current subblock,    -   a variable sbHeight specifying the height of the current        subblock,    -   the chroma reference sample array refPicLX_(C).        Output of this process is a predicted chroma sample value        predSampleLX_(C)        The variables shift1, shift2 and shift3 are derived as follows:    -   The variable shift1 is set equal to Min(4, BitDepth_(C)−8), the        variable shift2 is set equal to 6 and the variable shift3 is set        equal to Max(2, 14−BitDepth_(C)).    -   The variable picW_(C) is set equal to        pic_width_in_luma_samples/SubWidthC and the variable picH_(C) is        set equal to pic_height_in_luma_samples/SubHeightC.        The chroma interpolation filter coefficients fc[p] for each 1/32        fractional sample position p equal to xFrac_(C) or yFrac_(C) are        specified in Table 3.        The variable xOffset is set equal to        (sps_ref_wraparound_offset_minus1+1)*MinCbSizeY)/SubWidthC.        The chroma locations in full-sample units (xInt_(i), yInt_(i))        are derived as follows for i=0 . . . 3:    -   If subpic_treated_as_pic_flag[SubPicIdx] is equal to 1, the        following applies:

xInt_(i)=Clip3(SubPicLeftBoundaryPos/SubWidthC,SubPicRightBoundaryPos/SubWidthC,xInt_(L)+i)   (8-785)

yInt_(i)=Clip3(SubPicTopBoundaryPos/SubHeightC,SubPicBotBoundaryPos/SubHeightC,yInt_(L)+i)   (8-786)

-   -   Otherwise (subpic_treated_as_pic_flag[SubPicIdx] is equal to 0),        the following applies:

xInt_(i)=Clip3(0,picW_(C)−1,sps_ref_wraparound_enabled_flag?ClipH(xOffset,picW_(C),xInt_(C) +i−1): xInt_(C) +i−1)  (8-787)

yInt_(i)=Clip3(0,picH_(C)−1,yInt_(C) +i−1)  (8-788)

The chroma locations in full-sample units (xInt_(i), yInt_(i)) arefurther modified as follows for i=0 . . . 3:

xInt_(i)=Clip3(xSbInt_(C)−1,xSbInt_(C)+sbWidth+2,xInt_(i))  (8-789)

yInt_(i)=Clip3(ySbInt_(C)−1,ySbInt_(C)+sbHeight+2,yInt_(i))  (8-790)

The predicted chroma sample value predSampleLX_(C) is derived asfollows:

-   -   If both xFrac_(C) and yFrac_(C) are equal to 0, the value of        predSampleLX_(C) is derived as follows:

predSampleLX_(C)=refPicLX_(C) [xInt₁ ][yInt₁]<<shift3  (8-791)

-   -   Otherwise, if xFrac_(C) is not equal to 0 and yFrac_(C) is equal        to 0, the value of predSampleLX_(C) is derived as follows:

predSampleLX_(C)=(Σ_(i=0) ³ f _(C)[xFrac_(C) ][i]*refPicLX_(C) [xInt_(i)][yInt₁])>>shift1  (8-792)

-   -   Otherwise, if xFrac_(C) is equal to 0 and yFrac_(C) is not equal        to 0, the value of predSampleLX_(C) is derived as follows:

predSampleLX_(C)=(Σ_(i=0) ³ f _(C)[yFrac_(C) ][i]*refPicLX_(C) [xInt₁][yInt_(i)])>>shift1  (8-793)

-   -   Otherwise, if xFrac_(C) is not equal to 0 and yFrac_(C) is not        equal to 0, the value of predSampleLX_(C) is derived as follows:        -   The sample array temp[n] with n=0 . . . 3, is derived as            follows:

temp[n]=(Σ_(i=0) ³ f _(C)[xFrac_(C) ][i]*refPicLX_(C) [xInt_(i)][yInt_(n)])>>shift1  (8-794)

-   -   The predicted chroma sample value predSampleLX_(C) is derived as        follows:

yFrac_(C)yFrac_(C)yFrac_(C)yFrac_(C)predSampleLX_(C)=(f _(C)[][0]*temp[0]+yFrac_(C)yFrac_(C)yFrac_(C)yFrac_(C) f _(C)[][1]*temp[1]+yFrac_(C)yFrac_(C)yFrac_(C)yFrac_(C) f _(C)[][2]*temp[2]+yFrac_(C)yFrac_(C)yFrac_(C)yFrac_(C) c f _(C)[][3]*temp[3])>>shift2  (8-795)

TABLE 8-13 Specification of the chroma interpolation filter coefficientsf_(c)[p] for each 1/32 fractional sample position p. Fractional sampleinterpolation filter coefficients position p f_(c)[p][0] f_(c)[p][1]f_(c)[p][2] f_(c)[p][3] 1 −1 63 2 0 2 −2 62 4 0 3 −2 60 7 −1 4 −2 58 10−2 5 −3 57 12 −2 6 −4 56 14 −2 7 −4 55 15 −2 8 −4 54 16 −2 9 −5 53 18 −210 −6 52 20 −2 11 −6 49 24 −3 12 −6 46 28 −4 13 −5 44 29 −4 14 −4 42 30−4 15 −4 39 33 −4 16 −4 36 36 −4 17 −4 33 39 −4 18 −4 30 42 −4 19 −4 2944 −5 20 −4 28 46 −6 21 −3 24 49 −6 22 −2 20 52 −6 23 −2 18 53 −5 24 −216 54 −4 25 −2 15 55 −4 26 −2 14 56 −4 27 −2 12 57 −3 28 −2 10 58 −2 29−1 7 60 −2 30 0 4 62 −2 31 0 2 63 −1

2.5. Refined Sub-Block Based Affine Motion Compensated Prediction

The techniques disclosed herein include a method to refine the sub-blockbased affine motion compensated prediction with optical flow. After thesub-block based affine motion compensation is performed, predictionsample is refined by adding a difference derived by the optical flowequation, which is referred as prediction refinement with optical flow(PROF). The proposed method can achieve inter prediction in pixel levelgranularity without increasing the memory access bandwidth.

To achieve a finer granularity of motion compensation, this contributionproposes a method to refine the sub-block based affine motioncompensated prediction with optical flow. After the sub-block basedaffine motion compensation is performed, luma prediction sample isrefined by adding a difference derived by the optical flow equation. Theproposed PROF (prediction refinement with optical flow) is described asfollowing four steps.

-   -   Step 1) The sub-block-based affine motion compensation is        performed to generate sub-block prediction I(i, j).    -   Step2) The spatial gradients g_(x)(i, j) and g_(y)(i, j) of the        sub-block prediction are calculated at each sample location        using a 3-tap filter [−1, 0, 1].

g _(x)(i,j)=I(i+1,j)−I(i−1,j)

g _(y)(i,j)=I(i,j+1)−I(i,j−1)

The sub-block prediction is extended by one pixel on each side for thegradient calculation. To reduce the memory bandwidth and complexity, thepixels on the extended borders are copied from the nearest integer pixelposition in the reference picture. Therefore, additional interpolationfor padding region is avoided.

-   -   Step 3) The luma prediction refinement (denoted ΔI) as is        calculated by the optical flow equation.

ΔI(i,j)=g _(x)(i,j)*Δv _(x)(i,j)+g _(y)(i,j)*Δv _(y)(i,j)

where the delta MV (denoted as Δv(i, j)) is the difference between pixelMV computed for sample location (i, j), denoted by v(i, j), and thesub-block MV of the sub-block to which pixel (i,j) belongs, as shown inFIG. 1 .

Since the affine model parameters and the pixel location relative to thesub-block center are not changed from sub-block to sub-block, Δv(i,j)can be calculated for the first sub-block, and reused for othersub-blocks in the same CU. Let x and y be the horizontal and verticaloffset from the pixel location to the center of the sub-block, Δv(x, y)can be derived by the following equation,

$\{ \begin{matrix}{{\Delta v_{x}( {x,y} )} = {{c*x} + {d*y}}} \\{{\Delta v_{y}( {x,y} )} = {{e*x} + {f*y}}}\end{matrix} $

For 4-parameter affine model,

$\{ \begin{matrix}{c = {f = \frac{v_{1x} - v_{0x}}{w}}} \\{e = {{- d} = \frac{v_{1y} - v_{0y}}{w}}}\end{matrix} $

For 6-parameter affine model,

$\{ \begin{matrix}{c = \frac{v_{1x} - v_{0x}}{w}} \\{d = \frac{v_{2x} - v_{0x}}{h}} \\{e = \frac{v_{1y} - v_{0y}}{w}} \\{f = \frac{v_{2y} - v_{0y}}{h}}\end{matrix} $

where (v_(0x), v_(0y)), (v_(1x), v_(1y)), (v_(2x), v_(2y)) are thetop-left, top-right and bottom-left control point motion vectors, w andh are the width and height of the CU.

-   -   Step 4) Finally, the luma prediction refinement is added to the        sub-block prediction I(i,j). The final prediction I′ is        generated as the following equation.

I′(i,j)=I(i,j)+ΔI(i,j)

Some details are described below:

a) How to Derive the Gradients for PROF

In some embodiments, the gradients are calculated for each sub-block(4×4 sub-block in VTM-4.0) for each reference list. For each sub-block,the nearest integer samples of the reference block are fetched to padthe four side outer lines of samples.

Suppose the MV for the current sub-block is (MVx, MVy). Then thefractional part is calculated as (FracX, FracY)=(MVx&15, MVy&15). Theinteger part is calculated as (IntX, IntY)=(MVx>>4, MVy>>4). The offsets(OffsetX, OffsetY) are derived as:

OffsetX=FracX>7?1:0;

OffsetY=FracY>7?1:0;

Suppose the top-left coordinate of the current sub-block is (xCur, yCur)and the dimensions of the current sub-block is W×H. Then (xCor0, yCor0),(xCor1, yCor1), (xCor2, yCor2) and (xCor3, yCor3) are calculated as:

(xCor0,yCor0)=(xCur+IntX+OffsetX−1,yCur+IntY+OffsetY−1);

(xCor1,yCor1)=(xCur+IntX+OffsetX−1,yCur+IntY+OffsetY+H);

(xCor2,yCor2)=(xCur+IntX+OffsetX−1,yCur+IntY+OffsetY);

(xCor3,yCor3)=(xCur+IntX+OffsetX+W,yCur+IntY+OffsetY);

Suppose PredSample[x][y] with x=0 . . . W−1, y=0 . . . H−1 stores theprediction samples for the sub-block. Then the padding samples arederived as:

PredSample[x][−1]=(Ref(xCor0+x,yCor0)<<Shift0)−Rounding,for x=−1 . . .W;

PredSample[x][H]=(Ref(xCor1+x,yCor1)<<Shift0)−Rounding, for x=−1 . . .W;

PredSample[−1][y]=(Ref(xCor2,yCor2+y)<<Shift0)−Rounding, for y=0 . . .H−1;

PredSample[W][y]=(Ref(xCor3,yCor3+y)<<Shift0)−Rounding, for y=0 . . .H−1;

-   -   where Rec represents the reference picture. Rounding is an        integer, which is equal to 2¹³ in the exemplary PROF        implementation. Shift0=Max(2, (14−BitDepth));_PROF attempts to        increase the precision of the gradients, unlike BIO in VTM-4.0,        where the gradients are output with the same precision as input        luma samples.

The gradients in PROF are calculated as below:

Shift1=Shift0−4.

gradientH[x][y]=(predSamples[x+1][y]−predSample[x−1][y])>>Shift1

gradientV[x][y]=(predSample[x][y+1]−predSample[x][y−1])>>Shift1

It should be noted that predSamples[x][y] keeps the precision afterinterpolation.

b) How to Derive Δv for PROF

The derivation of Δv (denoted as dMvH[posX][posY] and dMvV[posX][posY]with posX=0 . . . W−1, posY=0 . . . H−1) can be described as below.

Suppose the dimensions of the current block is cbWidth x cbHeight, thenumber of control point motion vectors is numCpMv, and the control pointmotion vectors are cpMvLX[cpIdx], with cpIdx=0 . . . numCpMv−1 and Xbeing 0 or 1 representing the two reference lists.

The variables log 2CbW and log 2CbH are derived as follows:

log 2CbW=Log 2(cbWidth)

log 2CbH=Log 2(cbHeight)

The variables mvScaleHor, mvScaleVer, dHorX and dVerX are derived asfollows:

mvScaleHor=cpMvLX[0][0]<<7

mvScaleVer=cpMvLX[0][1]<<7

dHorX=(cpMvLX[1][0]−cpMvLX[0][0])<<(7−log 2CbW)

dVerX=(cpMvLX[1][1]−cpMvLX[0][1])<<(7−log 2CbW)

The variables dHorY and dVerY are derived as follows:

-   -   If numCpMv is equal to 3, the following applies:

dHorY=(cpMvLX[2][0]−cpMvLX[0][0])<<(7−log 2CbH)

dVerY=(cpMvLX[2][1]−cpMvLX[0][1])<<(7−log 2CbH)

-   -   Otherwise (numCpMv is equal to 2), the following applies:

dHorY=−dVerX

dVerY=dHorX

The variable qHorX, qVerX, qHorY and qVerY are derived as:

qHorX=dHorX<<2;

qVerX=dVerX<<2;

qHorY=dHorY<<2;

qVerY=dVerY<<2;

dMvH[0][0] and dMvV[0][0] are calculated as:

dMvH[0][0]=((dHorX+dHorY)<<1)−((qHorX+qHorY)<<1);

dMvV[0][0]=((dVerX+dVerY)<<1)−((qVerX+qVerY)<<1);

dMvH[xPos][0] and dMvV[xPos][0] for xPos from 1 to W−1 are derived as:

dMvH[xPos][0]=dMvH[xPos−1][0]+qHorX;

dMvV[xPos][0]=dMvV[xPos−1][0]+qVerX;

For yPos from 1 to H−1, the following applies:

dMvH[xPos][yPos]=dMvH[xPos][yPos−1]+qHorY with xPos=0 . . . W−1

dMvV[xPos][yPos]=dMvV[xPos][yPos−1]+qVerY with xPos=0 . . . W−1

Finally, dMvH[xPos][yPos] and dMvV[xPos][yPos] with posX=0 . . . W−1,posY=0 . . . H−1 are right shifted as:

dMvH[xPos][yPos]=SatShift(dMvH[xPos][yPos],7+2−1);

dMvV[xPos][yPos]=SatShift(dMvV[xPos][yPos],7+2−1);

where SatShift(x, n) and Shift (x,n) is defined as:

${{SatShift}( {x,n} )} = \{ \begin{matrix}{( {x + {{offsset}0}} )\operatorname{>>}n} & {if} & {x \geq 0} \\{- ( {( {{- x} + {{offset}1}} )\operatorname{>>}n} )} & {if} & {x < 0}\end{matrix} $Shift(x,n)=(x+offset0)>>n

In one example, offset0 and/or offset1 are set to (1<<n)>>1.

c) How to Derive ΔI for PROF

For a position (posX, posY) inside a sub-block, its corresponding Δv(i,j) is denoted as (dMvH[posX][posY], dMvV[posX][posY]). Its correspondinggradients are denoted as (gradientH[posX][posY], gradientV[posX][posY]).

Then ΔI(posX, posY) is derived as follows.

(dMvH[posX][posY], dMvV[posX][posY]) are clipped as:

dMvH[posX][posY]=Clip3(−32768,32767,dMvH[posX][posY]);

dMvV[posX][posY]=Clip3(−32768,32767,dMvV[posX][posY]);

ΔI(posX,posY)=dMvH[posX][posY]×gradientH[posX][posY]+dMvV[posX][posY]×gradientV[posX][posY];

ΔI(posX,posY)=Shift(ΔI(posX,posY),1+1+4);

ΔI(posX,posY)=Clip3(−(2¹³−1),2¹³−1,ΔI(posX,posY));

d) How to derive I′ for PROF

If the current block is not coded as bi-prediction orweighted-prediction,

I′(posX,posY)=Shift((I(posX,posY)+ΔI(posX,posY)),Shift0),

I′(posX,posY)=ClipSample(I′(posX,posY)),

-   -   where ClipSample clips a sample value to a valid output sample        value. Then I′(posX, posY) is output as the inter-prediction        value.

Otherwise (the current block is coded as bi-prediction orweighted-prediction). I′ (posX, posY) will be stored and used togenerate the inter-prediction value according to other prediction valuesand/or weighting values.

2.6. Example Slice Header

slice_header( ) { Descriptor  slice_pic_parameter_set_id ue(v)  if(rect_slice_flag || NumBricksInPic > 1 )   slice_address u(v)  if(!rect_slice_flag && !single_brick_per_slice_flag )  num_bricks_in_slice_minus1 ue(v)  non_reference_picture_flag u(1) slice_type ue(v)  if( separate_colour_plane_flag == 1 )  colour_plane_id u(2)  slice_pic_order_cnt_lsb u(v)  if( nal_unit_type== GDR_NUT)   recovery_poc_cnt ue(v)  if( nal_unit_type == IDR_W_RADL ||nal_unit_type == IDR_N_LP ||   nal_unit_type == CRA_NUT || NalUnitType== GDR_NUT )   no_output_of_prior_pics_flag u(1)  if(output_flag_present_flag )   pic_output_flag u(1)  if( ( nal_unit_type!= IDR_W_RADL && nal_unit_type != IDR_N_LP ) ||  sps_idr_rpl_present_flag ) {   for( i = 0; i < 2; i++ ) {   if(num_ref_pic_lists_in_sps[ i ]  >  0   &&   !pps_ref_pic_list_sps_idc[ i] &&      ( i == 0 || ( i = = 1 && rpl1_idx_present_flag ) ) )   ref_pic_list_sps_flag[ i ] u(1)   if( ref_pic_list_sps_flag[ i ] ) {   if( num_ref_pic_lists_in_sps[ i ] > 1 &&      ( i = = 0 || ( i = = 1&& rpl1_idx_present_flag ) ) )     ref_pic_list_idx[ i ] u(v)   } else   ref_pic_list_struct( i, num_ref_pic_lists_in_sps[ i ] )   for(j = 0;j < NumLtrpEntries[ i ][ RplsIdx[ i ] ]; j++ ) {    if(ltrp_in_slice_header_flag[ i ][ RplsIdx][ i ] ] )    slice_poc_lsb_lt[ i][ j ] u(v)    delta_poc_msb_present_flag[ i ][ j ] u(1)    if(delta_poc_msb_present_flag[ i ][ j ] )    delta_poc_msb_cycle_lt[ i ][ j] ue(v)   }  }  if( ( slice_type != I && num_ref_entries[ 0 ][RplsIdx [0 ] ] > 1 ) ||   ( slice_type == B && num_ref_entries[ 1 ][ RplsIdx[ 1 ]] > 1 ) ) {   num_ref_idx_active_override_flag u(1)   if(num_ref_idx_active_override_flag )    for( i = 0; i < ( slice_type == B? 2: 1 ); i++ )    if( num_ref_entries[ i ][ RplsIdx[ i ] ] > 1 )    num_ref_idx_active_minus1[ i ] ue(v)   }  }  if(partition_constraints_override_enabled_flag ) {  partition_constraints_override_flag ue(v)   if(partition_constraints_override_flag ) {  slice_log2_diff_min_qt_min_cb_luma ue(v)  slice_max_mtt_hierarchy_depth_luma ue(v)   if(slice_max_mtt_hierarchy_depth_luma !=0 )   slice_log2_diff_max_bt_min_qt_luma ue(v)   slice_log2_diff_max_tt_min_qt_luma ue(v)   }   if( slice_type == I &&qtbtt_dual_tree_intra_flag ) {    slice_log2_diff_min_qt_min_cb_chromaue(v)    slice_max_mtt_hierarchy_depth_chroma ue(v)    if(slice_max_mtt_hierarchy_depth_chroma != 0 )   slice_log2_diff_max_bt_min_qt_chroma ue(v)   slice_log2_diff_max_tt_min_qt_chroma ue(v)    }   }   }  }  if (slice_type != I ) {   if( sps_temporal_mvp_enabled_flag &&!pps_temporal_mvp_enabled_idc)   slice_temporal_mvp_enabled_flag u(1)  if( slice_type == B && !pps_mvd_l1_zero_idc)   mvd_l1_zero_flag u(1)  if( cabac_init_present_flag )   cabac_init_flag u(1)   if(slice_temporal_mvp_enabled_flag ) {   if( slice_type == B &&!pps_collocated_from_l0_idc )    collocated_from_l0_flag u(1)   if( (collocated_from_l0_flag && NumRefIdxActive[ 0 ] > 1 ) ||    (!collocated_from_l0_flag && NumRefIdxActive[ 1 ] > 1 ) )   collocated_ref_idx ue(v)   }   if(  (  pps_weighted_pred_flag   &&  slice_type   ==   P  )  ||   ( pps_weighted_bipred_flag && slice_type== B ) )   pred_weight_table( )   if(!pps_six_minus_max_num_merge_cand_plus1 )   six_minus_max_num_merge_candue(v)   if(       sps_affine_enabled_flag                 &&   !pps_five_minus_max_num_subblock_merge_cand_plus1 )  five_minus_max_num_subblock_merge_cand ue(v)   if(sps_fpel_mmvd_enabled_flag )   slice_fpel_mmvd_enabled_flag u(1)   if(sps_bdof_dmvr_slice_present_flag )   slice_disable_bdof_dmvr_flag u(1)  if(  sps_triangle_enabled_flag  &&  MaxNumMergeCand   >=   2   &&   !pps_max_num_merge_cand_minus_max_num_triangle_cand_minus1)  max_num_merge_cand_minus_max_num_triangle_cand ue(v)  }  if (sps_ibc_enabled_flag )   slice_six_minus_max_num_ibc_merge_cand ue(v) if( sps_joint_cbcr_enabled_flag )   slice_joint_cbcr_sign_flag u(1) slice_qp_delta se (v)  if( pps_slice_chroma_qp_offsets_present_flag ) {  slice_cb_qp_offset se (v)   slice_cr_qp_offset se (v)   if(sps_joint_cbcr_enabled_flag )   slice_joint_cbcr_qp_offset se (v)  } if( sps_sao_enabled_flag ) {   slice_sao_luma_flag u(1)   if(ChromaArrayType != 0 )   slice_sao_chroma_flag u(1)  }  if(sps_alf_enabled_flag ) {   slice_alf_enabled_flag u(1)   if(slice_alf_enabled_flag ) {   slice_num_alf_aps_ids_luma u(3)   for( i =0; i < slice_num_alf_aps_ids_luma; i++ )    slice_alf_aps_id_luma[ i ]u(3)   if( ChromaArrayType != 0 )    slice_alf_chroma_idc u(2)   if(slice_alf_chroma_idc )    slice_alf_aps_id_chroma u(3)   }  }  if (!pps_dep_quant_enabled_flag )   dep_quant_enabled_flag u(1)  if(!dep_quant_enabled_flag )   sign_data_hiding_enabled_flag u(1)  if(deblocking_filter_override_enabled_flag )  deblocking_filter_override_flag u(1)  if(deblocking_filter_override_flag ) {  slice_deblocking_filter_disabled_flag u(1)   if(!slice_deblocking_filter_disabled_flag ) {   slice_beta_offset_div2se(v)   slice_tc_offset_div2 se(v)   }  }  if( sps_lmcs_enabled_flag ) {  slice_lmcs_enabled_flag u(1)   if( slice_lmcs_enabled_flag ) {  slice_lmcs_aps_id u(2)   if( ChromaArrayType != 0 )   slice_chroma_residual_scale_flag u(1)   }  }  if(sps_scaling_list_enabled_flag ) {   slice_scaling_list_present_flag u(1)  if( slice_scaling_list_present_flag )   slice_scaling_list_aps_id u(3) }  if( entry_point_offsets_present_flag && NumEntryPoints > 0 ) {  offset_len_minus1 ue(v)   for( i = 0; i < NumEntryPoints; i++ )  entry_point_offset_minus1[ i ] u(v)  }  if(slice_header_extension_present_flag ) {   slice_header_extension_lengthue(v)   for( i = 0; i < slice_header_extension_length; i++)  slice_header_extension_data_byte[ i ] u(8)  }  byte_alignment( ) }

2.7. Example Sequence Parameter Set

Descriptor seq_parameter_set_rbsp( ) {  sps_decoding_parameter_set_idu(4)  sps_video_parameter_set_id u(4)  sps_max_sub_layers_minus1 u(3) sps_reserved_zero_5bits u(5) profile_tier_level(sps_max_sub_layers_minus1 )  gdr_enabled_flag u(1) sps_seq_parameter_set_id ue(v)  chroma_format_idc ue(v)  if(chroma_format_idc = = 3 )   separate_colour_plane_flag u(1) pic_width_max_in_luma_samples ue(v)  pic_height_max_in_luma_samplesue(v)  subpics_present_flag u(1)  if( subpics_present_flag) {  max_subpics_minus1 u(8)   subpic_grid_col_width_minus1 u(v)  subpic_grid_row_height_minus1 u(v)   for( i = 0; i <NumSubPicGridRows; i++ )    for( j = 0; j < NumSubPicGridCols; j++ )    subpic_grid_idx[ i ][ j ] u(v)   for( i = 0; i <= NumSubPics; i++ ){    subpic_treated_as_pic_flag[ i ] u(1)   loop_filter_across_subpic_enabled_flag[ i ] u(1)   }  } bit_depth_luma_minus8 ue(v)  bit_depth_chroma_minus8 ue(v) min_qp_prime_ts_minus4 ue(v)  log2_max_pic_order_cnt_lsb_minus4 ue(v) if( sps_max_sub_layers_minus1 > 0 )  sps_sub_layer_ordering_info_present_flag u(1)  for( i = (sps_sub_layer_ordering_info_present_flag ? 0 : sps_max_sub_layers_minus1);   i <= sps_max_sub_layers_minus1 ; i++ ) {  sps_max_dec_pic_buffering_minus1[ i ] ue(v)  sps_max_num_reorder_pics[ i ] ue(v)   sps_max_latency_increase_plus1[i ] ue(v)  }  long_term_ref_pics_flag u(1) inter_layer_ref_pics_present_flag u(1)  sps_idr_rpl_present_flag u(1) rpl1_same_as_rpl0_flag u(1)  for(i = 0; i < !rpl1_same_as_rpl0_flag ? 2: 1 ; i++ ) {   num_ref_pic_lists_in_sps[ i ] ue(v)   for(j = 0; j <num_ref_pic_lists_in_sps[ i ]; j++)    ref_pic_list_struct( i, j )  } if( ChromaArrayType != 0 )   qtbtt_dual_tree_intra_flag u(1) log2_ctu_size_minus5 u(2)  log2_min_luma_coding_block_size_minus2 ue(v) partition_constraints_override_enabled_flag u(1) sps_1og2_diff_min_qt_min_cb_intra_slice_luma ue(v) sps_1og2_diff_min_qt_min_cb_inter_slice ue(v) sps_max_mtt_hierarchy_depth_inter_slice ue(v) sps_max_mtt_hierarchy_depth_intra_slice_luma ue(v)  if(sps_max_mtt_hierarchy_depth_intra_slice_luma != 0 ) {  sps_log2_diff_max_bt_min_qt_intra_slice_luma ue(v)  sps_log2_diff_max_tt_min_qt_intra_slice_luma ue(v)  }  if(sps_max_mtt_hierarchy_depth_inter_slices != 0 ) {  sps_log2_diff_max_bt_min_qt_inter_slice ue(v)  sps_log2_diff_max_tt_min_qt_inter_slice ue(v)  }  if(qtbtt_dual_tree_intra_flag) {  sps_log2_diff_min_qt_min_cb_intra_slice_chroma ue(v)  sps_max_mtt_hierarchy_depth_intra_slice_chroma ue(v)   if (sps_max_mtt_hierarchy_depth_intra_slice_chroma != 0 ) {   sps_log2_diff_max_bt_min_qt_intra_slice_chroma ue(v)   sps_log2_diff_max_tt_min_qt_intra_slice_chroma ue(v)   }  } sps_max_luma_transform_size_64_flag u(1)  if( ChromaArrayType != 0 ) {  same_qp_table_for_chroma u(1)   for( i = 0; i <same_qp_table_for_chroma ? 1 : 3; i++ ) {   num_points_in_qp_table_minus1[ i ] ue(v)    for( j = 0; j <=num_points_in_qp_table_minus1[ i ]; j++ ) {     delta_qp_in_val_minus1[i ][ j ] ue(v)     delta_qp_out_val[ i ][ j ] ue(v)    }   }  } sps_weighted_pred_flag u(1)  sps_weighted_bipred_flag u(1) sps_sao_enabled_flag u(1)  sps_alf_enabled_flag u(1) sps_transform_skip_enabled_flag u(1)  if(sps_transform_skip_enabled_flag )   sps_bdpcm_enabled_flag u(1) sps_joint_cbcr_enabled_flag u(1)  sps_ref_wraparound_enabled_flag u(1) if( sps_ref_wraparound_enabled_flag )  sps_ref_wraparound_offset_minus1 ue(v)  sps_temporal_mvp_enabled_flagu(1)  if( sps_temporal_mvp_enabled_flag )   sps_sbtmvp_enabled_flag u(1) sps_amvr_enabled_flag u(1)  sps_bdof_enabled_flag u(1) sps_smvd_enabled_flag u(1)  sps_dmvr_enabled_flag u(1)  if(sps_bdof_enabled_flag | | sps_dmvr_enabled_flag)  sps_bdof_dmvr_slice_present_flag u(1)  sps_mmvd_enabled_flag u(1) sps_isp_enabled_flag u(1)  sps_mrl_enabled_flag u(1) sps_mip_enabled_flag u(1)  if( ChromaArrayType != 0 )  sps_cclm_enabled_flag u(1)   if( sps_cclm_enabled_flag &&chroma_format_idc = = 1 )   sps_cclm_colocated_chroma_flag u(1) sps_mts_enabled_flag u(1)  if( sps_mts_enabled_flag ) {  sps_explicit_mts_intra_enabled_flag u(1)  sps_explicit_mts_inter_enabled_flag u(1)  }  sps_sbt_enabled_flag u(1) if( sps_sbt_enabled_flag )   sps_sbt_max_size_64_flag u(1) sps_affine_enabled_flag u(1)  if( sps_affine_enabled_flag ) {  sps_affine_type_flag u(1)   sps_affine_amvr_enabled_flag u(1)  sps_affine_prof_enabled_flag u(1)  }  if( chroma_format_idc = = 3 )  sps_palette_enabled_flag u(1)  sps_bcw_enabled_flag u(1) sps_ibc_enabled_flag u(1)  sps_ciip_enabled_flag u(1)  if(sps_mmvd_enabled_flag )   sps_fpel_mmvd_enabled_flag u(1) sps_triangle_enabled_flag u(1)  sps_lmcs_enabled_flag u(1) sps_lfnst_enabled flag u(1)  sps_ladf_enabled_flag u(1)  if (sps_ladf_enabled_flag ) {   sps_num_ladf_intervals_minus2 u(2)  sps_ladf_lowest_interval_qp_offset se (v)   for( i = 0; i <sps_num_ladf_intervals_minus2 + 1; i++ ) {    sps_ladf_qp_offset[ i ] se(v)    sps_ladf_delta_threshold_minus1[ i ] ue (v)   }  } sps_scaling_list_enabled_flag u(1)  hrd_parameters_present_flag u(1) if( general_hrd_parameters_present_flag ) {   num_units_in_tick u(32)  time_scale u(32)   sub_layer_cpb_parameters_present_flag u(1)   if(sub_layer_cpb_parameters_present_flag )    general_hrd_parameters( 0,sps_max_sub_layers_minus1 )   else    general_hrd_parameters(sps_max_sub_layers_minus1, sps_max_sub_layers_minus1 )  } vui_parameters_present_flag u(1)  if( vui_parameters_present_flag )  vui_parameters( )  sps_extension_flag u(1)  if( sps_extension_flag )  while( more_rbsp_data( ) )   sps_extension_data_flag u(1) rbsp_trailing_bits( ) }

2.8 Example Picture Parameter Set

Descriptor pic_parameter_set_rbsp( ) {  pps_pic_parameter_set_id ue(v) pps_seq_parameter_set_id ue(v)  pic_width_in_luma_samples ue(v) pic_height_in_luma_samples ue(v)  conformance_window_flag u(1)  if(conformance_window_flag ) {   conf_win_left_offset ue(v)  conf_win_right_offset ue(v)   conf_win_top_offset ue(v)  conf_win_bottom_offset ue(v)  }  output_flag_present_flag u(1) single_tile_in_pic_flag u(1)  if( !single_tile_in_pic_flag ) {  uniform_tile_spacing_flag u(1)   if( uniform_tile_spacing_flag ) {   tile_cols_width_minus1 ue(v)    tile_rows_height_minus1 ue(v)   }else {    num_tile_columns_minus1 ue(v)    num_tile_rows_minus1 ue(v)   for( i = 0; i < num_file_columns_minus1; i++ )    tile_column_width_minus1[ i ] ue(v)    for( i = 0; i <num_tile_rows_minus1; i++ )     tile_row_height_minus1[ i ] ue(v)   }  brick_splitting_present_flag u(1)   if( uniform_tile_spacing_flag &&brick_splitting_present_flag )    num_tiles_in_pic_minus1 ue(v)   for( i= 0; brick_splitting_present_flag && i <= num_tiles_in_pic_minus1 + 1;i++ ) {    if( RowHeight[ i ] > 1 )     brick_split_flag[ i ] u(1)   if( brick_split_flag[ i ] ) {     if( RowHeight[ i ] > 2 )     uniform_brick_spacing_flag[ i ] u(1)     if(uniform_brick_spacing_flag[ i ] )      brick_height_minus1[ i ] ue(v)    else {      num_brick_rows_minus2[ i ] ue(v)     for( j = 0; j <=num_brick_rows_minus2[ i ]; j++ )      brick_row_height_minus1[ i ][ j ]ue(v)     }    }   }   single_brick_per_slice_flag u(1)   if(!single_brick_per_slice_flag )    rect_slice_flag u(1)   if(rect_slice_flag && !single_brick_per_slice_flag ) {   num_slices_in_pic_minus1 ue(v)   bottom_right_brick_idx_length_minus1 ue(v)    for( i = 0; i <num_slices_in_pic_minus1; i++ ) {     bottom_right_brick_idx_delta[ i ]u(v)     brick_idx_delta_sign_flag[ i ] u(1)    }   }  loop_filler_across_bricks_enabled_flag u(1)   if(loop_filter_across_bricks_enabled_flag )  loop_filler_across_slices_enabled_flag u(1)  }  if( rect_slice_flag) {  signalled_slice_id_flag u(1)   if( signalled_slice_id_flag ) {   signalled_slice_id_length_minus1 ue(v)    for( i = 0; i <=num_slices_in_pic_minus1; i++ )     slice_id[ i ] u(v)   }  } entropy_coding_sync_enabled_flag u(1)  if( !single_tile_in_pic_flag | |entropy_coding_sync_enabled_flag )   entry_point_offsets_present_flagu(1)  cabac_init_present_flag u(1)  for( i = 0; i < 2; i++ )  num_ref_idx_default_active_minus1[ i ] ue(v)  rpl1_idx_present_flagu(1)  init_qp_minus26 se(v)  if( sps_transform_skip_enabled_flag )  log2_transform_skip_max_size_minus2 ue(v)  cu_qp_delta_enabled_flagu(1)  if( cu_qp_delta_enabled_flag )   cu_qp_delta_subdiv ue(v) pps_cb_qp_offset se(v)  pps_cr_qp_offset se(v) pps_joint_cbcr_qp_offset se(v) pps_slice_chroma_qp_offsets_present_flag u(1) cu_chroma_qp_offset_enabled_flag u(1)  if(cu_chroma_qp_offset_enabled_flag ) {   cu_chroma_qp_offset_subdiv ue(v)  chroma_qp_offset_list_len_minus1 ue(v)   for( i = 0; i <=chroma_qp_offset_list_len_minus1; i++ ) {    cb_qp_offset_list[ i ]se(v)    cr_qp_offset_list[ i ] se(v)    joint_cbcr_qp_offset_list[ i ]se(v)   }  }  pps_weighted_pred_flag u(1)  pps_weighted_bipred_flag u(1) deblocking_filter_control_present_flag u(1)  if(deblocking_filter_control_present_flag ) {  deblocking_filter_override_enabled_flag u(1)  pps_deblocking_filter_disabled_flag u(1)   if(!pps_deblocking_filter_disabled_flag ) {    pps_beta_offset_div2 se(v)   pps_tc_offset_div2 se(v)   }  } constant_slice_header_params_enabled_flag u(1)  if(constant_slice_header_params_enabled_flag ) {  pps_dep_quant_enabled_idc u(2)   for( i = 0; i < 2; i++ )   pps_ref_pic_list_sps_idc[ i ] u(2)   pps_temporal_mvp_enabled_idcu(2)   pps_mvd_l1_zero_idc u(2)   pps_collocated_from_l0_idc u(2)  pps_six_minus_max_num_merge_cand_plus1 ue(v)  pps_five_minus_max_num_subblock_merge_cand_plus1 ue(v)  pps_max_num_merge_cand_minus_max_num_triangle_cand_minus1 ue(v)  } pps_loop_filter_across_virtual_boundaries_disabled_flag u(1)  if(pps_loop_filter_across_virtual_boundaries_disabled_flag ) {  pps_num_ver_virtual_boundaries u(2)   for( i = 0; i <pps_num_ver_virtual_boundaries; i++ )    pps_virtual_boundaries_pos_x[ i] u(13)   pps_num_hor_virtual_boundaries u(2)   for( i = 0; i <pps_num_hor_virtual_boundaries; i++ )    pps_virtual_boundaries_pos_y[ i] u(13)  }  slice_header_extension_present_flag u(1)  pps_extension_flagu(1)  if( pps_extension_flag )   while( more_rbsp_data( ) )   pps_extension_data_flag u(1)  rbsp_trailing_bits( ) }

2.9. Example Adaptive Parameter Set

Descriptor adaptation_parameter_set_rbsp( ) { adaptation_parameter_set_id u(5)  aps_params_type u(3)  if(aps_params_type = = ALF_APS )   alf_data( )  else if( aps_params_type == LMCS_APS )   lmcs_data( )  else if( aps_params_type = = SCALING_APS )  scaling_list_data( )  aps_extension_flag u(1)  if( aps_extension_flag)   while( more_rbsp_data( ) )    aps_extension_data_flag u(1) rbsp_trailing_bits( ) } Descriptor alf_data( ) { alf_luma_filter_signal_flag u(1)  alf_chroma_filter_signal_flag u(1) if( alf_luma_filter_signal_flag ) {   alf_luma_clip_flag u(1)  alf_luma_num_filters_signalled_minus1 ue(v)   if(alf_luma_num_filters_signalled_minus1 > 0 ) {    for( filtIdx = 0;filtIdx < NumAlfFilters; filtIdx++ )     alf_luma_coeff_delta_idx[filtIdx ] u(v)   }   alf_luma_coeff_signalled_flag u(1)   if(alf_luma_coeff_signalled_flag ) {    for( sfIdx = 0; sfIdx <=alf_luma_num_filters_signalled_minus1 ; sfIdx++ )    alf_luma_coeff_flag[ sfIdx ] u(1)   }   for( sfIdx = 0; sfIdx <=alf_luma_num_filters_signalled_minus1 ; sfIdx++ ) {    if(alf_luma_coeff_flag[ sfIdx ] ) {     for( j = 0; j < 12; j++ ) {     alf_luma_coeff_abs[ sfIdx ][ j ] uek(v)      if( alf_luma_coeffabs[ sfIdx ][ j ] )       alf_luma_coeff_sign[ sfIdx ][ j ] u(1)     }   }   }   if( alf_luma_clip_flag ) {    for( sfIdx = 0; sfIdx <=alf_luma_num_filters_signalled_minus1; sfIdx++ ) {     if(alf_luma_coeff_flag[ sfIdx ] ) {      for( j = 0; j < 12; j++ )      alf_luma_clip_idx[ sfIdx ][ j ] u(2)     }    }   }  }  if(alf_chroma_filter_signal_flag ) {   alf_chroma_num_alt_filters_minus1ue(v)    for( altIdx = 0; altIdx <= alf_chroma_num_alt_filters_minus1;altIdx++ ) {    alf_chroma_clip_flag[ altIdx ] u(1)    for( j = 0; j <6; j++ ) {     alf_chroma_coeff_abs[ altIdx ][ j ] uek(v)     if(alf_chroma_coeff_abs[ altIdx ][ j ] > 0 )      alf_chroma_coeff_sign[altIdx ][ j ] u(1)    }    if( alf_chroma_clip_flag[ altIdx ] ) {    for( j = 0; j < 6; j++ )      alf_chroma_clip_idx[ altIdx ][ j ]u(2)    }   }  } } Descriptor lmcs_data ( ) {  lmcs_min_bin_idx ue(v) lmcs_delta_max_bin_idx ue(v)  lmcs_delta_cw_prec_minus1 ue(v)  for ( i= lmcs_min_bin_idx; i <= LmcsMaxBinIdx; i++ ) {   lmcs_delta_abs_cw[ i ]u(v)   if ( lmcs_delta_abs_cw[ i ] ) > 0 )    lmcs_delta_sign_cw_flag[ i] u(1)  } } Descriptor scaling_list_data( ) {  for( sizeId = 1; sizeId <7; sizeId++ )   for( matrixId = 0; matrixId < 6; matrixId++ ) {    if( !( ( ( sizeId = = 1 ) && ( matrixId % 3 = = 0 ) ) | |     ( ( sizeId = =6) && ( matrixId % 3 != 0 ) ) ) ) {     scaling_list_pred_mode_flag[sizeId ][ matrixId ] u(1)     if( !scaling_list_pred_mode_flag[ sizeId][ matrixId ] )      scaling_list_pred_matrix_id_delta[ sizeId ][matrixId ] ue(v)     else {      nextCoef = 8      coefNum = Min( 64, (1<< ( sizeId << 1 ) ) )      if( sizeId > 3 ) {      scaling_list_dc_coef_minus8[ sizeId − 4 ][ matrixId ] se(v)      nextCoef = scaling_list_dc_coef_minus8[ sizeId − 4 ][ matrixId ] +8      }      for( i = 0; i < coefNum; i++ ) {       x = DiagScanOrder[3 ][ 3 ][ i ][ 0 ]       y = DiagScanOrder[ 3 ][ 3 ][ i ][ 1 ]       if( !( sizeId = = 6 && x >= 4 && y >= 4) ) {       scaling_list_delta_coef se(v)        nextCoef = ( nextCoef +scaling_list_delta_coef + 256 ) % 256        ScalingList[ sizeId ][matrixId [ i ] = nextCoef       }      }     }    }   }  } }

2.10. Example Picture Header

In some embodiments, the picture header is designed to have thefollowing properties:

-   -   1. Temporal Id and layer Id of picture header NAL unit are the        same as temporal Id and layer Id of layer access unit that        contains the picture header.    -   2. Picture header NAL unit shall precede NAL unit containing the        first slice of its associated picture. This established the        association between a picture header and slices of picture        associated with the picture header without the need of having        picture header Id signalled in picture header and referred to        from slice header.    -   3. Picture header NAL unit shall follow picture level parameter        sets or higher level such as DPS, VPS, SPS, PPS, etc. This        consequently requires those parameter sets to be not        repeated/present within a picture or within an access unit.    -   4. Picture header contains information about picture type of its        associated picture. The picture type may be used to define the        following (not an exhaustive list)        -   a. The picture is an IDR picture        -   b. The picture is a CRA picture        -   c. The picture is a GDR picture        -   d. The picture is a non-IRAP, non-GDR picture and contains            I-slices only        -   e. The picture is a non-IRAP, non-GDR picture and may            contain P- and I-slices only        -   f. The picture is a non-IRAP, non-GDR picture and contains            any of B-, P-, and/or I-slices    -   5. Move signalling of picture level syntax elements in slice        header to picture header.    -   6. Signal non-picture level syntax elements in slice header that        are typically the same for all slices of the same picture in        picture header. When those syntax elements are not present in        picture header, they may be signalled in slice header.

In some implementations, a mandatory picture header concept is used tobe transmitted once per picture as the first VCL NAL unit of a picture.It is also proposed to move syntax elements currently in the sliceheader to this picture header. Syntax elements that functionally onlyneed to be transmitted once per picture could be moved to the pictureheader instead of being transmitted multiple times for a given picture,e.g., syntax elements in the slice header are transmitted once perslice. Moving slice header syntax elements constrained to be the samewithin a picture

The syntax elements are already constrained to be the same in all slicesof a picture. It is asserted that moving these fields to the pictureheader so they are signalled only once per picture instead of once perslice avoids unnecessary redundant transmission of bits without anychange to the functionality of these syntax elements.

1. In Some Implementations, there is the Following Semantic Constraint:

When present, the value of each of the slice header syntax elementsslice_pic_parameter_set_id, non_reference_picture_flag, colour_plane_id,slice_pic_order_cnt_lsb, recovery_poc_cnt, no_output_of_prior_pics_flag,pic_output_flag, and slice_temporal_mvp_enabled_flag shall be the samein all slice headers of a coded picture. Thus each of these syntaxelements could be moved to the picture header to avoid unnecessaryredundant bits.

The recovery_poc_cnt and no_output_of_prior_pics_flag are not moved tothe picture header in this contribution. Their presence in the sliceheader is dependent on a conditional check of the slice headernal_unit_type, so they are suggested to be studied if there is a desireto move these syntax elements to the picture header.

2. In Some Implementations, there are the Following SemanticConstraints:

When present, the value of slice_lmcs_aps_id shall be the same for allslices of a picture.

When present, the value of slice_scaling_list_aps_id shall be the samefor all slices of a picture. Thus each of these syntax elements could bemoved to the picture header to avoid unnecessary redundant bits.

In some embodiments, the syntax elements are not currently constrainedto be the same in all slices of a picture. It is suggested to assess theanticipated usage of these syntax elements to determine which can bemoved into the picture header to simplify the overall VVC design as itis claimed there is a complexity impact to processing a large number ofsyntax elements in every slice header.

-   -   1. The following syntax elements are proposed to be moved to the        picture header. There are currently no restrictions on them        having different values for different slices but it is claimed        there is no/minimal benefit and coding loss to transmitting them        in every slice header as their anticipated usage would change at        the picture level:        -   a. six_minus_max_num_merge_cand        -   b. five_minus_max_num_subblock_merge_c and        -   c. slice_fpel_mmvd_enabled_flag        -   d. slice_disable_bdof_dmvr_flag        -   e. max_num_merge_cand_minus_max_num_triangle_cand        -   f. slice_six_minus_max_num_ibc_merge_cand    -   2. The following syntax elements are proposed to be moved to the        picture header. There are currently no restrictions on them        having different values for different slices but it is claimed        there is no/minimal benefit and coding loss to transmitting them        in every slice header as their anticipated usage would change at        the picture level:        -   a. partition_constraints_override_flag        -   b. slice_log 2_diff min_qt_min_cb_luma        -   c. slice_max_mtt_hierarchy_depth_luma        -   d. slice_log 2_diff_max_bt_min_qt_luma        -   e. slice_log 2_diff_max_tt_min_qt_luma        -   f. slice_log 2_diff_min_qt_min_cb_chroma        -   g. slice_max_mtt_hierarchy_depth_chroma        -   h. slice_log 2_diff_max_bt_min_qt_chroma        -   i. slice_log 2_diff_max_tt_min_qt_chroma

The conditional check “slice_type==I” associated with some of thesesyntax elements has been removed with the move to the picture header.

-   -   3. The following syntax elements are proposed to be moved to the        picture header. There are currently no restrictions on them        having different values for different slices but it is claimed        there is no/minimal benefit and coding loss to transmitting them        in every slice header as their anticipated usage would change at        the picture level:        -   a. mvd_l1_zero_flag

The conditional check “slice_type==B” associated with some of thesesyntax elements has been removed with the move to the picture header.

-   -   4. The following syntax elements are proposed to be moved to the        picture header. There are currently no restrictions on them        having different values for different slices but it is claimed        there is no/minimal benefit and coding loss to transmitting them        in every slice header as their anticipated usage would change at        the picture level:        -   a. dep_quant_enabled_flag        -   b. sign_data_hiding_enabled_flag

2.10.1 Example Syntax Tables 7.3.2.8 Picture Header RBSP Syntax

Descriptor picture_header_rbsp( ) {  non_reference_picture_flag u(1) gdr_pic_flag u(1)  no_output_of_prior_pics_flag u(1)  if( gdr_pic_flag)   recovery_poc_cnt ue(v)  ph_pic_parameter_set_id ue(v)  if(sps_subpic_id_present_flag && !sps_subpic_id_signalling_flag ) {  ph_subpic_id_signalling_present_flag u(1)   if(ph_subpics_id_signalling_present_flag ) {    ph_subpic_id_len_minus1ue(v)    for( i = 0; i < NumSubPics; i++ )     ph_subpic_id[ i ] u(v)  }  }  if(!sps_loop_filter_across_virtual_boundaries_disabled_present_flag ) {  ph_loop_filter_across_virtual_boundaries_disabled_present_flag u(1)  if( ph_loop_filter_across_virtual_boundaries_disabled_present_flag ) {   ph_num_ver_virtual_boundaries u(2)    for( i = 0; i <ph_num_ver_virtual_boundaries; i++ )     ph_virtual_boundaries_pos_x[ i] u(13)    ph_num_hor_virtual_boundaries u(2)    for( i = 0; i <ph_num_hor_virtual_boundaries; i++ )     ph_virtual_boundaries_pos_y[ i] u(13)   }  }  if( separate_colour_plane_flag = = 1 )   colour_plane_idu(2)  if( output_flag_present_flag )   pic_output_flag u(1) pic_rpl_present_flag u(1)  if( pic_rpl_present_flag) {   for( i = 0; i< 2; i++ ) {    if( num_ref_pic_lists_in_sps[ i ] > 0 &&!pps_ref_pic_list_sps_idc[ i ] &&      (i = = 0 | | (i = = 1 &&rpl1_idx_present_flag ) ) )     pic_rpl_sps_flag[ i ] u(1)    if(pic_rpl_sps_flag[ i ] ) {     if( num_ref_pic_lists_in_sps[ i ] > 1 &&      (i = = 0 | | (i = = 1 && rpl1_idx_present_flag ) ) )    pic_rpl_idx[ i ] u(v)    } else     ref_pic_list_struct( i,num_ref_pic_lists_in_sps[ i ] )    for( j = 0; j < NumLtrpEntries[ i ][RplsIdx[ i ] ]; j++ ) {     if(ltrp_in_slice_header_flag[ i ][ RplsIdx[i ] ] )      pic_poc_lsb_lt[ i ][ j ] u(v)    pic_delta_poc_msb_present_flag[ i ][ j ] u(1)     if(pic_delta_poc_msb_present_flag[ i ][ j ] )     pic_delta_poc_msb_cycle_lt[ i ][ j ] ue(v)    }   }  }  if(partition_constraints_override_enabled_flag ) {  partition_constraints_override_flag ue(v)   if(partition_constraints_override_flag) {   pic_log2_diff_min_qt_min_cb_intra_slice_luma ue(v)   pic_log2_diff_min_qt_min_cb_inter_slice ue(v)   pic_max_mtt_hierarchy_depth_inter_slice ue(v)   pic_max_mtt_hierarchy_depth_intra_slice_luma ue(v)    if(pic_max_mtt_hierarchy_depth_intra_slice_luma !=0 ) {    pic_log2_diff_max_bt_min_qt_intra_slice_luma ue(v)    pic_log2_diff_max_tt_min_qt_intra_slice_luma ue(v)    }    if(pic_max_mtt_hierarchy_depth_inter_slice != 0 ) {    pic_log2_diff_max_bt_min_qt_inter_slice ue(v)    pic_log2_diff_max_tt_min_qt_inter_slice ue(v)    }    if(qtbtt_dual_tree_intra_flag ) {    pic_log2_diff_min_qt_min_cb_intra_slice_chroma ue(v)    pic_max_mtt_hierarchy_depth_intra_slice_chroma ue(v)     if(pic_max_mtt_hierarchy_depth_intra_slice_chroma != 0 ) {     pic_log2_diff_max_bt_min_qt_intra_slice_chroma ue(v)     pic_log2_diff_max_tt_min_qt_intra_slice_chroma ue(v)     }    }   } }  if( cu_qp_delta_enabled_flag ) {  pic_cu_qp_delta_subdiv_intra_slice ue(v)  pic_cu_qp_delta_subdiv_inter_slice ue(v)  }  if(cu_chroma_qp_offset_enabled_flag ) {  pic_cu_chroma_qp_offset_subdiv_intra_slice ue(v)  pic_cu_chroma_qp_offset_subdiv_inter_slice ue(v)  }  if(sps_temporal_mvp_enabled_flag && !pps_temporal_mvp_enabled_idc )  pic_temporal_mvp_enabled_flag u(1)  if(!pps_mvd_l1_zero_idc)  mvd_l1_zero_flag u(1)  if( !pps_six_minus_max_num_merge_cand_plus1 )  pic_six_minus_max_num_merge_cand ue(v)  if( sps_affine_enabled_flag &&   !pps_five_minus_max_num_subblock_merge_cand_plus1 )  pic_five_minus_max_num_subblock_merge_cand ue(v)  if(sps_fpel_mmvd_enabled_flag )   pic_fpel_mmvd_enabled_flag u(1)  if(sps_bdof_dmvr_slice_present_flag )   pic_disable_bdof_dmvr_flag u(1) if( sps_triangle_enabled_flag && MaxNumMergeCand >= 2 &&   !pps_max_num_merge_cand_minus_max_num_triangle_cand_minus1 )  pic_max_num_merge_cand_minus_max_num_triangle_cand ue(v)  if (sps_ibc_enabled_flag )   pic_six_minus_max_num_ibc_merge_cand ue(v)  if(sps_joint_cbcr_enabled_flag )   pic_joint_cbcr_sign_flag u(1)  if(sps_sao_enabled_flag ) {   pic_sao_enabled_present_flag u(1)   if(pic_sao_enabled_present_flag ) {    pic_sao_luma_enabled_flag u(1)   if(ChromaArrayType != 0 )     pic_sao_chroma_enabled_flag u(1)   }  } if( sps_alf_enabled_flag ) {   pic_alf_enabled_present_flag u(1)   if(pic_alf_enabled_present_flag ) {    pic_alf_enabled_flag u(1)    if(pic_alf_enabled_flag ) {     pic_num_alf_aps_ids_luma u(3)     for( i =0; i < pic_num_alf_aps_ids_luma; i++ )      pic_alf_aps_id_luma[ i ]u(3)     if( ChromaArrayType != 0 )      pic_alf_chroma_idc u(2)     if(pic_alf_chroma_idc )      pic_alf_aps_id_chroma u(3)    }   }  }  if (!pps_dep_quant_enabled_flag )   pic_dep_quant_enabled_flag u(1)  if(!pic_dep_quant_enabled_flag )   sign_data_hiding_enabled_flag u(1)  if(deblocking_filter_override_enabled_flag ) {  pic_deblocking_filter_override_present_flag u(1)   if(pic_deblocking_filter_override_present_flag ) {   pic_deblocking_filter_override_flag u(1)    if(pic_deblocking_filter_override_flag ) {    pic_deblocking_filter_disabled_flag u(1)     if(!pic_deblocking_filter_disabled_flag ) {      pic_beta_offset_div2 se(v)     pic_tc_offset_div2 se(v)     }    }   }  }  if(sps_lmcs_enabled_flag ) {   pic_lmcs_enabled_flag u(1)   if(pic_lmcs_enabled_flag ) {    pic_lmcs_aps_id u(2)    if( ChromaArrayType!= 0 )     pic_chroma_residual_scale_flag u(1)   }  }  if(sps_scaling_list_enabled_flag ) {   pic_scaling_list_present_flag u(1)  if( pic_scaling_list_present_flag )    pic_scaling_list_aps_id u(3)  } if( picture_header_extension_present_flag ) {   ph_extension_lengthue(v)   for( i = 0; i < ph_extension_length; i++)   ph_extension_data_byte[ i ] u(8)  }  rbsp_trailing_bits( ) }

2.11. Example DMVR

Decoder-side Motion Vector Refinement (DMVR) utilizes the bilateralmatching (BM) to derive motion information of the current CU by findingthe closest match between two blocks along the motion trajectory of thecurrent CU in two different reference pictures. The BM method calculatesthe distortion between the two candidate blocks in the reference picturelist L0 and list L1. As illustrated in FIG. 1 , the SAD between the redblocks based on each MV candidate around the initial MV is calculated.The MV candidate with the lowest SAD becomes the refined MV and used togenerate the bi-predicted signal. The cost function used in the matchingprocess is row-subsampled SAD (sum of absolute difference). An examplein FIG. 7 .

In VTM5.0, DMVR is adopted to refine motion vectors (MVs) at the decoderfor a coding unit (CU) when the CU is coded with regular merge/skip modeand bi-prediction, one reference picture is before the current pictureand the other reference picture is after the current picture in displayorder, the temporal distance between the current picture and onereference picture is equal to that between the current picture and theother reference picture, and the bi-prediction with CU weights (BCW)selects equal weights. When DMVR is applied, one luma coding block (CB)is divided into several independently processed subblocks of sizemin(cbWidth,16)×min(cbHeight,16). DMVR refines MVs of each subblock byminimizing the SAD between 1/2-subsampled 10-bit L0 and L1 predictionsamples generated by bilinear interpolation. For each subblock, integerΔMV search around the initial MVs (i.e., the MVs of the selected regularmerge/skip candidate) is first performed using SAD, and then fractionalΔMV derivation is performed to obtain the final MVs.

BDOF refines the luma prediction samples for a CU when the CU is codedwith bi-prediction, one reference picture is before the current pictureand the other reference picture is after the current picture in displayorder, and BCW selects equal weights. The eight-tap interpolation isused for generating the initial L0 and L1 prediction samples accordingto the input MVs (e.g., final MVs of DMVR in case of enabling DMVR).Next, a two-level early termination process is performed. The firstearly termination is at subblock level, and the second early terminationis at 4×4 block level and is checked when the first early terminationdoes not occur. At each level, the SAD between full-sampled 14-bit L0and L1 prediction samples in each subblock/4×4 block is calculatedfirst. If the SAD is smaller than one threshold, BDOF is not applied tothe subblock/4×4 block. Otherwise, BDOF parameters are derived and usedto generate the final luma sample predictors for each 4×4 block. InBDOF, the subblock size is the same as that in DMVR, i.e.,min(cbWidth,16)×min(cbHeight,16).

When the CU is coded with regular merge/skip mode, one reference pictureis before the current picture and the other reference picture is afterthe current picture in display order, the temporal distance between thecurrent picture and one reference picture is equal to that between thecurrent picture and the other reference picture, and BCW selects equalweights, DMVR and BDOF are both applied. The flow of cascading DMVR andBDOF processes is shown in FIG. 8 .

FIG. 8 shows the flow of cascading DMVR and BDOF processes in VTM5.0.The DMVR SAD operations and BDOF SAD operations are different and notshared.

In order to reduce the latency and operations in this critical path,when DMVR and BDOF are both applied, the latest VVC working draft hasbeen revised to reuse the subblock SAD calculated in DMVR for thesubblock early termination in BDOF.

The SAD calculation is defined as follows:

sad = ∑ nSbW - 1 x = 0 ∑ n ⁢ S ⁢ b ⁢ H / 2 - 1 y = 0 abs ⁢  ( pL ⁢ 0 [ x +2 + d ⁢ X ] [ 2 * y + 2 + dY ] - pL ⁢ 1 [ x + 2 - d ⁢ X ] [ 2 * y + 2 - d ⁢Y ] )

-   -   wherein two variables nSbW and nSbH specifying the width and the        height of the current subblock, two (nSbW+4)×(nSbH+4) arrays pL0        and pL1 containing the predicted samples for L0 and L1        respectively, and the integer sample offset (dX, dY) in        prediction list L0.

To reduce the penalty of the uncertainty of DMVR refinement, it isproposed to favor the original MV during the DMVR process. The SADbetween the reference blocks referred by the initial (or calledoriginal) MV candidate is decreased by 1/4 of the SAD value. That is,when both dX and dY in above equation are equal to 0, the value of sadis modified as follows:

sad=sad−(sad>>2)

When the SAD value is smaller than a threshold (2*subblockwidth*subblock height), there is no need to perform BDOF anymore.

3. Drawbacks of Existing Implementations

DMVR and BIO do not involve the original signal during refining themotion vectors, which may result in coding blocks with inaccurate motioninformation. Also, DMVR and BIO sometimes employ the fractional motionvectors after the motion refinements while screen videos usually haveinteger motion vectors, which makes the current motion information moreinaccurate and make the coding performance worse.

When RPR is applied in VVC, RPR (ARC) may have the following problems:

-   -   1. With RPR, the interpolation filters may be different for        adjacent samples in a block, which is undesirable in SIMD        (Single Instruction Multiple Data) implementation.    -   2. The bounding region does not consider RPR.    -   3. It is noted that “The conformance cropping window offset        parameters are only applied at the output. All internal decoding        processes are applied to the uncropped picture size.” However,        those parameters may be used in the decoding process when RPR is        applied.    -   4. When deriving the reference sample position, RPR only        considers the ratio between two conformance windows. But the        top-left offset difference between two conformance windows        should also be considered.    -   5. The ratio between the width/height of a reference picture and        that of the current picture is constrained in VVC. However, the        ratio between the width/height of the conformance window of a        reference picture and that of the conformance window of the        current picture is not constrained.    -   6. Not all the syntax elements are handled properly in the        picture header.    -   7. In current VVC, for TPM, GEO prediction mode, the chroma        blending weights are derived regardless of the chroma sample        location type of a video sequence. For example, in TPM/GEO, if        chroma weights are derived from luma weights, the luma weights        may be needed to be downsampled to match the sampling of the        chroma signal. The chroma downsampling are normally applied        assumes the chroma sample location type 0, which is widely used        in ITU-R BT.601 or ITU-R BT.709 container. However, if a        different chroma sample location type is used, this could result        in a misalignment between the chroma samples and the downsampled        luma samples, which may reduce the coding performance.    -   8. It is noted that the SAD calculation/SAD threshold doesn't        consider the bit-depth impact. Therefore, for higher bit-depth        (e.g., 14 or 16 bits input sequences), the threshold for the        early termination may be too small.    -   9. For the non-RPR case, ΔMVR with 1/2-pel MV precision (i.e.,        alternative interpolation filter/switchable interpolation        filter) is applied with a 6-tap motion compensation filter but        8-tap is applied to other cases (e.g., 1/16-pel). However, for        the RPR case, the same interpolation filter is applied to all        cases without considering the mv/mvd precision. Therefore, the        signaling of 1/2-pel case (alternative interpolation        filter/switchable interpolation filter) is wasting bits.    -   10. The decision of partition tree splitting is allowed or not        is dependent on the coded picture resolution instead of output        picture resolution.    -   11. SMVD/MMVD are applied which doesn't consider RPR cases.        These methods are based on the assumption that symmetric MVD are        applied for two reference pictures. However, when output picture        resolution are different, such an assumption is not true.    -   12. Pairwise merge candidate is generated by averaging two MVs        from two merge candidates in the same reference picture list.        However, when the two reference pictures associated with two        merge candidates are with different resolution, the averaging        doesn't make sense.

4. Example Techniques and Embodiments

The detailed embodiments described below should be considered asexamples to explain general concepts. These embodiments should not beinterpreted narrowly way. Furthermore, these embodiments can be combinedin any manner.

The methods described below may be also applicable to other decodermotion information derivation technologies in addition to the DMVR andBIO mentioned below.

A motion vector is denoted by (mv_x, mv_y) wherein mv_x is thehorizontal component and mv_y is the vertical component.

In this disclosure, the resolution (or dimensions, or width/height, orsize) of a picture may refer to the resolution (or dimensions, orwidth/height, or size) of the coded/decoded picture, or may refer to theresolution (or dimensions, or width/height, or size) of the conformancewindow in the coded/decoded picture. In one example, the resolution (ordimensions, or width/height, or size) of a picture may refer to thatparameters that related to RPR (reference picture resampling) process,such as the scaling window/phase offset window. In one example, theresolution (or dimensions, or width/height, or size) of a picture isrelated to that associated with the output picture.

Motion Compensation in RPR

-   -   1. When the resolution of the reference picture is different to        the current picture, or when the width and/or height of the        reference picture is larger that of the current picture,        predicted values for a group of samples (at least two samples)        of a current block may be generated with the same horizontal        and/or vertical interpolation filter.        -   a. In one example, the group may comprise all samples in a            region of the block.            -   i. For example, a block may be divided into S M×N                rectangles not overlapped with each other. Each M×N                rectangle is a group. In an example as shown in FIG. 2 ,                a 16×16 block can be divided into 16 4×4 rectangles,                each of which is a group.            -   ii. For example, a row with N samples is a group. N is                an integer no larger than the block width. In one                example, N is 4 or 8 or the block width.            -   iii. For example, a column with N samples is a group. N                is an integer no larger than the block height. In one                example, N is 4 or 8 or the block height.            -   iv. M and/or N may be pre-defined or derived on-the-fly,                such as based on block dimension/coded information or                signaled.        -   b. In one example, samples in the group may have the same MV            (denoted as shared MV).        -   c. In one example, samples in the group may have MVs with            the same horizontal component (denoted as shared horizontal            component).        -   d. In one example, samples in the group may have MVs with            the same vertical component (denoted as shared vertical            component).        -   e. In one example, samples in the group may have MVs with            the same fractional part of the horizontal component            (denoted as shared fractional horizontal component).            -   i. For example, suppose the MV for a first sample is                (MV1x, MV1y) and the MV for a second sample is (MV2x,                MV2y), it should be satisfied that MV1x & (2^(M)−1) is                equal to MV2x & (2^(M)−1), where M denotes MV precision.                For example, M=4.        -   f. In one example, samples in the group may have MVs with            the same fractional part of the vertical component (denoted            as shared fractional vertical component).            -   i. For example, suppose the MV for a first sample is                (MV1x, MV1y) and the MV for a second sample is (MV2x,                MV2y), it should be satisfied that MV1y & (2^(M)−1) is                equal to MV2y & (2^(M)−1), where M denotes MV precision.                For example, M=4.        -   g. In one example, for a sample in the group to be            predicted, the motion vector, denoted by MV_(b), may be            firstly derived according to the resolutions of the current            picture and the reference picture (e.g. (refx_(L), refy_(L))            derived in 8.5.6.3.1 in JVET-O2001-v14). Then, MV_(b) may be            further modified (e.g., being rounded/truncated/clipped) to            MV′ to satisfy the requirements such as the above bullets,            and MV′ will be used to derive the prediction sample for the            sample.            -   i. In one example, MV′ has the same integer part as                MV_(b), and the fractional part of the MV′ is set to be                the shared fractional horizontal and/or vertical                component.            -   ii. In one example, MV′ is set to be the one with the                shared fractional horizontal and/or vertical component,                and closest to MV_(b).        -   h. The shared motion vector (and/or shared horizontal            component and/or shared vertical component and/or shared            fractional vertical component and/or shared fractional            vertical component) may be set to be the motion vector            (and/or horizontal component and/or vertical component            and/or fractional vertical component and/or fractional            vertical component) of a specific sample in the group.            -   i. For example, the specific sample may be at a corner                of a rectangle-shaped group, such as “A”, “B’, “C” and                “D” shown in FIG. 3A.            -   ii. For example, the specific sample may be at a center                of a rectangle-shaped group, such as “E”, “F’, “G” and                “H” shown in FIG. 3A.            -   iii. For example, the specific sample may be at an end                of a row-shaped or column-shaped group, such as “A” and                “D” shown in FIGS. 3B and 3C.            -   iv. For example, the specific sample may be at a middle                of a row-shaped or column-shaped group, such as “B” and                “C” shown in FIGS. 3B and 3C.            -   v. In one example, the motion vector of the specific                sample may be the MV_(b) mentioned in bullet g.        -   i. The shared motion vector (and/or shared horizontal            component and/or shared vertical component and/or shared            fractional vertical component and/or shared fractional            vertical component) may be set to be the motion vector            (and/or horizontal component and/or vertical component            and/or fractional vertical component and/or fractional            vertical component) of a virtual sample located at a            different position compared to all samples in this group.            -   i. In one example, the virtual sample is not in the                group, but it locates in the region covering all samples                in the group.                -   1) Alternatively, the virtual sample is located                    outside the region covering all samples in the                    group, e.g., next to the bottom-right position of                    the region.            -   ii. In one example, the MV of a virtual sample is                derived in the same way as a real sample but with                different positions.            -   iii. “V” in FIGS. 3A-3C shows three examples of virtual                samples.        -   j. The shared MV (and/or shared horizontal component and/or            shared vertical component and/or shared fractional vertical            component and/or shared fractional vertical component) may            be set to be a function of MVs (and/or horizontal components            and/or vertical components and/or fractional vertical            components and/or fractional vertical components) of            multiple samples and/or virtual samples.            -   i. For example, the shared MV (and/or shared horizontal                component and/or shared vertical component and/or shared                fractional vertical component and/or shared fractional                vertical component) may be set to be the average of MVs                (and/or horizontal components and/or vertical components                and/or fractional vertical components and/or fractional                vertical components) of all or partial of samples in the                group, or of sample “E”, “F”, “G”, “H” in FIG. 3A, or of                sample “E”, “H” in FIG. 3A, or of sample “A”, “B”, “C”,                “D” in FIG. 3A, or of sample “A”, “D” in FIG. 3A, or of                sample “B”, “C” in FIG. 3B, or of sample “A”, “D” in                FIG. 3B, or of sample “B”, “C” in FIG. 3C, or of sample                “A”, “D” in FIG. 3C,    -   2. It is proposed that only integer MVs are allowed to perform        the motion compensation process to derive the prediction block        of a current block when the resolution of the reference picture        is different to the current picture, or when the width and/or        height of the reference picture is larger that of the current        picture.        -   a. In one example, the decoded motion vectors for samples to            be predicted are rounded to integer MVs before being used.        -   b. In one example, the decoded motion vector for samples to            be predicted are rounded to the integer MV that is closest            to the decoded motion vector.        -   c. In one example, the decoded motion vector for samples to            be predicted are rounded to the integer MV that is closest            to the decoded motion vector in horizontal direction.        -   d. In one example, the decoded motion vector for samples to            be predicted are rounded to the integer MV that is closest            to the decoded motion vector in vertical direction.    -   3. The motion vectors used in the motion compensation process        for samples in a current block (e.g., shared MV/shared        horizontal or vertical or fractional component/MV′ mentioned in        above bullets) may be stored in the decoded picture buffer and        utilized for motion vector prediction of succeeding blocks in        current/different pictures.        -   a. Alternatively, the motion vectors used in the motion            compensation process for samples in a current block (e.g.,            shared MV/shared horizontal or vertical or fractional            component/MV′ mentioned in above bullets) may be disallowed            to be utilized for motion vector prediction of succeeding            blocks in current/different pictures.            -   i. In one example, the decoded motion vectors (e.g.,                MV_(b) in above bullets) may be utilized for motion                vector prediction of succeeding blocks in                current/different pictures.        -   b. In one example, the motion vectors used in the motion            compensation process for samples in a current block may be            utilized in the filtering process (e.g., deblocking            filter/SAO/ALF).            -   i. Alternatively, the decoded motion vectors (e.g.,                MV_(b) in above bullets) may be utilized in the                filtering process.        -   c. In one example, such MV may be derived at sub-block level            and may be stored for each sub-block.    -   4. It is proposed that the interpolation filters used in the        motion compensation process to derive the prediction block of a        current block may be selected depending on whether the        resolution of the reference picture is different to the current        picture, or whether the width and/or height of the reference        picture is larger that of the current picture.        -   a. In one example, the interpolation filters with less taps            may be applied when condition A is satisfied, wherein            condition A depends on the dimensions of the current picture            and/or the reference picture.            -   i. In one example, condition A is the resolution of the                reference picture is different to the current picture.            -   ii. In one example, condition A is the width and/or                height of the reference picture is larger than that of                the current picture.            -   iii. In one example, condition A is W1>a*W2 and/or                H1>b*H2, wherein (W1, H1) represents the width and                height of the reference picture and (W2, H2) represents                the width and height of the current picture, a and b are                two factors, e.g. a=b=1.5.            -   iv. In one example, condition A may also depend on                whether bi-prediction is used.            -   v. In one example, 1-tap filters are applied. In other                words, an integer pixel without filtering is output as                the interpolation result.            -   vi. In one example, bi-linear filters are applied when                the resolution of the reference picture is different to                the current picture.            -   vii. In one example, 4-tap filters or 6-tap filters are                applied when the resolution of the reference picture is                different to the current picture, or the width and/or                height of the reference picture is larger than that of                the current picture.                -   1) The 6-tap filters may also be used for the affine                    motion compensation.                -   2) The 4-tap filters may also be used for                    interpolation for chroma samples.        -   b. In one example, padding samples are used to perform            interpolation when the resolution of the reference picture            is different to the current picture, or the width and/or            height of the reference picture is larger that of the            current picture.        -   c. Whether to and/or how to apply the methods disclosed in            bullet 4 may depend on the color components.            -   i. For example, the methods are only applied on the luma                component.        -   d. Whether to and/or how to apply the methods disclosed in            bullet 4 may depend on the interpolation filtering            direction.            -   i. For example, the methods are only applied on                horizontal filtering.            -   ii. For example, the methods are only applied on                vertical filtering.    -   5. It is proposed that a two-stage process for prediction block        generation is applied when the resolution of the reference        picture is different to the current picture, or when the width        and/or height of the reference picture is larger that of the        current picture.        -   a. In the first stage, a virtual reference block is            generated by up-sampling or down-sampling a region in the            reference picture depending on width and/or height of the            current picture and the reference picture.        -   b. In the second stage, the prediction samples are generated            from the virtual reference block by applying interpolation            filtering, independent of width and/or height of the current            picture and the reference picture.    -   6. It is proposed that the calculation of top-left coordinate of        the bounding block for reference sample padding (xSbInt_(L),        ySbInt_(L)) as in some embodiments may be derived depending on        width and/or height of the current picture and the reference        picture.        -   a. In one example, the luma locations in full-sample units            are modified as:

xInt_(i)=Clip3(xSbInt_(L) −Dx,xSbInt_(L)+sbWidth+Ux,xInt_(i)),

yInt_(i)=Clip3(ySbInt_(L) −Dy,ySbInt_(L)+sbHeight+Uy,yInt_(i)),

-   -    where Dx and/or Dy and/or Ux and/or Uy may depend on width        and/or height of the current picture and the reference picture.        -   b. In one example, the chroma locations in full-sample units            are modified as:

xInti=Clip3(xSbInt_(C) −Dx,xSbInt_(C)+sbWidth+Ux,xInti)

yInti=Clip3(ySbInt_(C) −Dy,ySbInt_(C)+sbHeight+Uy,yInti)

-   -    where Dx and/or Dy and/or Ux and/or Uy may depend on width        and/or height of the current picture and the reference picture.    -   7. Instead of storing/using the motion vectors for a block based        on the same reference picture resolution as current picture, it        is proposed to use the real motion vectors with the resolution        difference taken into consideration.        -   a. Alternatively, furthermore, when using the motion vector            to generate the prediction block, there is no need to            further change the motion vector according to the            resolutions of the current picture and the reference picture            (e.g. (refx_(L), refy_(L))).

Interaction Between RPR and Other Coding Tools

-   -   8. Whether to/how to apply filtering process (e.g., deblocking        filter) may depend on the resolutions of reference pictures        and/or the resolution of the current picture.        -   a. In one example, the boundary strength (BS) settings in            the deblocking filters may take the resolution differences            into consideration in addition to motion vector differences.            -   i. In one example, the scaled motion vector difference                according to the current and reference pictures'                resolutions may be used to determine the boundary                strength.        -   b. In one example, the strength of deblocking filter for a            boundary between block A and block B may be set differently            (e.g., being increased/decreased) if the resolution of at            least one reference picture of block A is different to (or            smaller than or larger than) the resolution of at least one            reference picture of block B compared to the case that same            resolutions are utilized for the two blocks.        -   c. In one example, a boundary between block A and block B is            marked as to be filtered (e.g., BS is set to 2) if the            resolution of at least one reference picture of block A is            different to (or smllar than or larger than) the resolution            of at least one reference picture of block B.        -   d. In one example, the strength of deblocking filter for a            boundary between block A and block B may be set differently            (e.g., being increased/decreased) if the resolution of at            least one reference picture of block A and/or block B is            different to (or smaller than or larger than) the resoltuion            of the current picture compared to the case same resolution            is utilized of the reference picture and current picture.        -   e. In one example, a boundary between two blocks is marked            to be filtered (e.g., BS is set to 2) if at least one            reference picture of at least one block of the two has a            resolution different to that of the current picture.    -   9. When a sub-picture exists, a conformance bitstream may should        satisfy the reference picture must have the same resolution as        the current picture.        -   a. Alternatively, when a reference picture has a different            resolution to the current picture, there must be no            sub-picture in the current picture.        -   b. Alternatively, for a sub-picture in the current picture,            it is disallowed to use a reference picture that is with            different resolution as the current picture.            -   i. Alternatively, furthermore, the reference picture                management may be invoked to exclude those reference                pictures with different resolutions.    -   10. In one example, sub-pictures (e.g., how to split one picture        to multiple sub-pictures) may be defined separately for pictures        with different resolutions.        -   In one example, the corresponding sub-picture in the            reference picture can be derived by scaling and/or            offsetting a sub-picture of the current picture, if the            reference picture has a different resolution to the current            picture.    -   11. PROF (prediction refinement with optical flow) may be        enabled when the reference picture has a resolution different to        that of the current picture.        -   a. In one example, one set of MV (denoted as MV_(g)) may be            generated for a group of samples and may be used for motion            compensation as described in bullet 1. On the other hand, MV            (denoted as MV_(p)) may be derived for each sample, and the            difference (e.g., corresponds to the Δv used in PROF)            between the MV_(p) and MV_(g) together with the gradients            (e.g., spatial gradients of the motion compensated blocks)            may be used for deriving the prediction refinement.        -   b. In one example, MV_(p) may be with a different precision            from MV_(g). For example, MV_(p) may be with 1/N-pel (N>0)            precision, N=32, 64 etc.        -   c. In one example, MV_(g) may be with a different precision            form the internal MV precision (e.g., 1/16-pel).        -   d. In one example, the prediction refinement is added to the            prediction block to generate refined prediction block.        -   e. In one example, such method may be applied in each            prediction direction.        -   f. In one example, such method may be applied only in            uni-prediction case.        -   g. In one example, such method may be applied in            uni-prediction or/and bi-prediction.        -   h. In one example, such method may be applied only when the            reference picture has a different resolution from the            current picture.    -   12. It is proposed that only one MV may be utilized for a        block/sub-block to perform the motion compensation process to        derive the prediction block of a current block when the        resolution of the reference picture is different to that of the        current picture.        -   a. In one example, the only MV for the block/sub-block may            be defined as a function (e.g., average) of all MVs            associated with each sample within the block/sub-block.        -   b. In one example, the only MV for the block/sub-block may            be defined as a selected MV associated with a selected            sample (e.g., center sample) within the block/sub-block.        -   c. In one example, only one MV may be utilized a 4×4 block            or subblock (e.g., 4×1).        -   d. In one example, BIO may be further applied to compensate            the precision loss due to a block-based motion vector.    -   13. A lazy mode without signalling any block-based motion        vectors may be applied when the width and/or height of the        reference picture is different from that of the current picture.        -   a. In one example, no motion vectors may be signaled and the            motion compensation process is to approximate the case of a            pure resolution change of a still image.        -   b. In one example, only a motion vector at            picture/tile/brick/CTU level may be signal and related            blocks may use the motion vector when resolution changes.    -   14. PROF may be applied to approximate motion compensation when        the width and/or height of the reference picture is different to        that of the current picture for blocks coded with affine        prediction mode and/or non-affine prediction mode.        -   a. In one example, PROF may be enabled when the width and/or            height of the reference picture and that of the current            picture are different.        -   b. In one example, a set of affine motions may be generated            by combining the indicated motion and resolution scaling and            used by PROF.    -   15. Interweaved prediction (e.g. as proposed in JVET-K0102) may        be applied to approximate motion compensation when the width        and/or height of the reference picture is different to that of        the current picture.        -   a. In one example, resolution change (zooming) is            represented as an affine motion, and interweaved motion            prediction may be applied.    -   16. LMCS and/or chroma residual scaling may be disabled when the        width and/or height of the current picture is different to that        of the TRAP picture in a same TRAP period.        -   a. In one example, when LMCS is disabled, the slice level            flags such as slice_lmcs_enabled_flag, slice_lmcs_aps_id,            and slice_chroma_residual_scale_flag may be not signaled and            inferred to be 0.        -   b. In one example, when chroma residual scaling is disabled,            the slice level flags such as            slice_chroma_residual_scale_flag may be not signaled and            inferred to be 0.

Constrains on RPR

-   -   17. RPR may be applied to coding blocks with block dimensions        constrains.        -   a. In one example, for an M×N coding block, with M as the            block width and N as the block height, when M*N<T or M*N<=T            (such as T=256), RPR may be not used.        -   b. In one example, when M<K (or M<=K) (such as K=16) and/or            N<L (or N<=L) (such as L=16), RPR may be not used.    -   18. Bitstream conformance may be added to restrict the ratio        between the width and/or height of an active reference picture        (or its conformance window) and that of the current picture (or        its conformance window). Suppose refPicW and refPicH denote the        width and height of reference picture, curPicW and curPicH        denote the width and height of current picture,        -   a. In one example, when (refPicW÷curPicW) is equal to an            integer number, the reference picture may be marked as            active reference picture.            -   i. Alternatively, when (refPicW÷curPicW) is equal to a                factional number, the reference picture may be marked as                not available.        -   b. In one example, when (refPicW÷curPicW) is equal to (X*n),            where X denotes a fractional number such as X=1/2, and n            denotes an integer number such as n=1, 2, 3, 4 . . . , the            reference picture may be marked as active reference picture.            -   i. In one example, when (refPicW curPicW) is not equal                to (X*n), the reference picture may be marked as not                available.    -   19. Whether to and/or how to enable a coding tool (e.g.,        bi-prediction/the whole triangular prediction mode        (TPM)/blending process in TPM) for a M×N block may depend on the        resolutions of reference pictures (or their conformance windows)        and/or that of the current picture (or its conformance window).        -   a. In one example, M*N<T or M*N<=T (such as T=64).        -   b. In one example, M<K (or M<=K) (such as K=16) and/or N<L            (or N<=L) (such as L=16).        -   c. In one example, the coding tool is not allowed when            width/height of at least one reference picture is different            to the current picture,            -   i. In one example, the coding tool is not allowed when                width/height of at least one reference picture of the                block is larger that of the current picture.        -   d. In one example, the coding tool is not allowed when            width/height of each reference picture of the block is            different to that of the current picture,            -   i. In one example, the coding tool is not allowed when                width/height of each reference pictures is larger that                of the current picture.        -   e. Alternatively, furthermore, when the coding tool is not            allowed, motion compensation may be conducted with one MV as            a uni-prediction.

Conformance Window Related

-   -   20. The conformance cropping window offset parameters (e.g.,        conf_win_left_offset) are signaled in N-pel precision instead of        1-pel wherein N is an positive integer greater than 1.        -   a. In one example, the actual offset may be derived as the            signaled offset multiplied by N.        -   b. In one example, N is set to 4 or 8.    -   21. It is proposed that the conformance cropping window offset        parameters are not only applied at the output. Certian internal        decoding processes may depend on the cropped picture size (e.g.,        the resolution of a conformance window in a picture).    -   22. It is proposed that the conformance cropping window offset        parameters in a first video unit (e.g. PPS) and in a second        video unit may be different when the width and/or height of a        picture denoted as (pic_width_in_luma_samples,        pic_height_in_luma_samples) in the first video unit and second        video unit are the same.    -   23. It is proposed that the conformance cropping window offset        parameters in a first video unit (e.g. PPS) and in a second        video unit should be the same in a conformance bitstream when        the width and/or height of a picture denoted as        (pic_width_in_luma_samples, pic_height_in_luma_samples) in the        first video unit and second video unit are different.        -   a. It is proposed that the conformance cropping window            offset parameters in a first video unit (e.g. PPS) and in a            second video unit should be the same in a conformance            bitstream no matter the width and/or height of a picture            denoted as (pic_width_in_luma_samples,            pic_height_in_luma_samples) in the first video unit and            second video unit are the same or not.    -   24. Suppose the width and height of the conformance window        defined in a first video unit (e.g. PPS) are denoted as W1 and        H1, respectively. The width and height of the conformance window        defined in a second video unit (e.g. PPS) are denoted as W2 and        H2, respectively. The top-left position of the conformance        window defined in a first video unit (e.g. PPS) are denoted as        X1 and Y1. The top-left position of the conformance window        defined in a second video unit (e.g. PPS) are denoted as X2 and        Y2. The width and height of the coded/decoded picture (e.g.        pic_width_in_luma_samples and pic_height_in_luma_samples)        defined in a first video unit (e.g. PPS) are denoted as PW1 and        PH1, respectively. The width and height of the coded/decoded        picture defined in a second video unit (e.g. PPS) are denoted as        PW2 and PH2.        -   a. In one example, W1/W2 should be equal to X1/X2 in a            conformance bitstream.            -   i. Alternatively, W1/X1 should be equal to W2/X2 in a                conformance bitstream.            -   ii. Alternatively, W1*X2 should be equal to W2*X1 in a                conformance bitstream.        -   b. In one example, H1/H2 should be equal to Y1/Y2 in a            conformance bitstream.            -   i. Alternatively, H1/Y1 should be equal to H2/Y2 in a                conformance bitstream.            -   ii. Alternatively, H1*Y2 should be equal to H2*Y1 in a                conformance bitstream.        -   c. In one example, PW1/PW2 should be equal to X1/X2 in a            conformance bitstream.            -   i. Alternatively, PW1/X1 should be equal to PW2/X2 in a                conformance bitstream.            -   ii. Alternatively, PW1*X2 should be equal to PW2*X1 in a                conformance bitstream.        -   d. In one example, PH1/PH2 should be equal to Y1/Y2 in a            conformance bitstream.            -   i. Alternatively, PH1/Y1 should be equal to PH2/Y2 in a                conformance bitstream.            -   ii. Alternatively, PH1*Y2 should be equal to PH2*Y1 in a                conformance bitstream.        -   e. In one example, PW1/PW2 should be equal to W1/W2 in a            conformance bitstream.            -   i. Alternatively, PW1/W1 should be equal to PW2/W2 in a                conformance bitstream.            -   ii. Alternatively, PW1*W2 should be equal to PW2*W1 in a                conformance bitstream.        -   f. In one example, PH1/PH2 should be equal to H1/H2 in a            conformance bitstream.            -   i. Alternatively, PH1/H1 should be equal to PH2/H2 in a                conformance bitstream.            -   ii. Alternatively, PH1*H2 should be equal to PH2*H1 in a                conformance bitstream.        -   g. In a conformance bitstream, if PW1 is greater than PW2,            W1 must be greater than W2.        -   h. In a conformance bitstream, if PW1 is smaller than PW2,            W1 must be smaller than W2.        -   i. In a conformance bitstream, (PW1−PW2)*(W1−W2) must be no            smaller than 0.        -   j. In a conformance bitstream, if PH1 is greater than PH2,            H1 must be greater than H2.        -   k. In a conformance bitstream, if PH1 is smaller than PH2,            H1 must be smaller than H2.        -   l. In a conformance bitstream, (PH1−PH2)*(H1−H2) must be no            smaller than 0.        -   m. In a conformance bitstream, W1/W2 must be no larger than            (or smaller than) PW1/PW2 if PW1>=PW2.        -   n. In a conformance bitstream, H1/H2 must be no larger than            (or smaller than) PH1/PH2 if PH1>=PH2.    -   25. Suppose the width and height of the conformance window of        the current picture are denoted as W and H, respectively. The        width and height of the conformance window of a reference        picture are denoted as W′ and H′, respectively. Then at least        one constraint below should be followed by a conformance        bit-stream.        -   a. W*pw>=W′; pw is an integer such as 2.        -   b. W*pw>W′; pw is an integer such as 2.        -   c. W′ *pw′>=W; pw′ is an integer such as 8.        -   d. W′ *pw′>W; pw′ is an integer such as 8.        -   e. H*ph>=H′; ph is an integer such as 2.        -   f. H*ph>H′; ph is an integer such as 2.        -   g. H′ *ph′>=H; ph′ is an integer such as 8.        -   h. H′ *ph′>H; ph′ is an integer such as 8.        -   i. In one example, pw is equal to pw′.        -   j. In one example, ph is equal to ph′.        -   k. In one example, pw is equal to ph.        -   l. In one example, pw′ is equal to ph′.        -   m. In one example, the above sub-bullets may be required to            be satisfied by a conformance bitstream when W and H            represent the width and height of the current picture,            respectively. W′ and H′ represent the width and height of a            reference picture.    -   26. It is proposed that the conformance window parameters are        partially signaled.        -   a. In one example, the top-left sample in a conformance            window of a picture is the same one as that in the picture.        -   b. For example, conf_win_left_offset as defined in VVC is            not signaled and inferred to be zero.        -   c. For example, conf_win_top_offset as defined in VVC is not            signaled and inferred to be zero.    -   27. It is proposed that the derivation of the position (e.g.        (refx_(L), refy_(L)) as defined in VVC) of a reference sample        may depend on the top-left position (e.g. (conf_win_left_offset,        conf_win_top_offset) as defined in VVC) of the conformance        window of the current picture and/or the reference picture. FIG.        4 shows examples of the samples positions derived as in VVC (a)        and in a proposed method (b). Dashed rectangles represent the        conformance windows.        -   a. In one example, the dependency exists only when the width            and/or the height of the current picture and that of the            reference picture are different.        -   b. In one example, the derivation of the horizontal position            (e.g. refx_(L) as defined in VVC) of a reference sample may            depend on the left position (e.g. conf_win_left_offset as            defined in VVC) of the conformance window of the current            picture and/or the reference picture.            -   i. In one example, the horizontal position (denoted as                xSb′) of the current sample relative to the top-left                position of the conformance window in the current                picture is calculated and used to derive the position of                the reference sample.                -   1) For example,                    xSb′=xSb−(conf_win_left_offset<<Prec) is calculated                    and used to derive the position of the reference                    sample, wherein xSb represents the horizontal                    position of the current sample in the current                    picture. conf_win_left_offset represents the                    horizontal position of the top-left sample in the                    conformance window of the current picture. Prec                    presents the precision of xSb and xSb′ wherein                    (xSb>>Prec) may show the actual horizontal                    coordinate of current sample relative to the current                    picture. For example, Prec=0 or Prec=4.            -   ii. In one example, horizontal position (denoted as Rx′)                of the reference sample relative to the top-left                position of the conformance window in the reference                picture is calculated.                -   1) The calculation of Rx′ may depend on xSb′, and/or                    a motion vector, and/or a resampling ratio.            -   iii. In one example, horizontal position (denoted as Rx)                of the reference sample relative in the reference                picture is calculated depending on Rx′.                -   1) For example,                    Rx=Rx′+(conf_win_left_offset_ref<<Prec) is                    calculated, wherein conf_win_left_offset_ref                    represents the horizontal position of the top-left                    sample in the conformance window of the reference                    picture. Prec presents the precision of Rx and Rx′.                    For example, Prec=0 or Prec=4.            -   iv. In one example, Rx may be calculated directly                depending on xSb′, and/or a motion vector, and/or a                resampling ratio. In other words, the two steps of                derivation on Rx′ and Rx are combined into a one-step                calculation.            -   v. Whether to and/or how to use the left position (e.g.                conf_win_left_offset as defined in VVC) of the                conformance window of the current picture and/or the                reference picture may depend on the color components                and/or color formats.                -   1) For example, conf_win_left_offset may be revised                    as                    conf_win_left_offset=conf_win_left_offset*SubWidthC,                    wherein SubWidthC defines the horizontal sampling                    step of a color component. E.g., SubWidthC is equal                    to 1 for the luma component. SubWidthC is equal to 2                    for a chroma component when the color format is                    4:2:0 or 4:2:2.                -   2) For example, conf_win_left_offset may be revised                    as                    conf_win_left_offset=conf_win_left_offset/SubWidthC,                    wherein SubWidthC defines the horizontal sampling                    step of a color component. E.g., SubWidthC is equal                    to 1 for the luma component. SubWidthC is equal to 2                    for a chroma component when the color format is                    4:2:0 or 4:2:2.        -   c. In one example, the derivation of the vertical position            (e.g. refy_(L) as defined in VVC) of a reference sample may            depend on the top position (e.g. conf_win_top_offset as            defined in VVC) of the conformance window of the current            picture and/or the reference picture.            -   i. In one example, the vertical position (denoted as                ySb′) of the current sample relative to the top-left                position of the conformance window in the current                picture is calculated and used to derive the position of                the reference sample.                -   1) For example,                    ySb′=ySb−(conf_win_top_offset<<<Prec) is calculated                    and used to derive the position of the reference                    sample, wherein ySb represents the vertical position                    of the current sample in the current picture.                    conf_win_top_offset represents the vertical position                    of the top-left sample in the conformance window of                    the current picture. Prec presents the precision of                    ySb and ySb′. For example, Prec=0 or Prec=4.            -   ii. In one example, the vertical position (denoted as                Ry′) of the reference sample relative to the top-left                position of the conformance window in the reference                picture is calculated.                -   1) The calculation of Ry′ may depend on ySb′, and/or                    a motion vector, and/or a resampling ratio.            -   iii. In one example, the vertical position (denoted as                Ry) of the reference sample relative in the reference                picture is calculated depending on Ry′.                -   1) For example,                    Ry=Ry′+(conf_win_top_offset_ref<<Prec) is                    calculated, wherein conf_win_top_offset_ref                    represents the vertical position of the top-left                    sample in the conformance window of the reference                    picture. Prec presents the precision of Ry and Ry′.                    For example, Prec=0 or Prec=4.            -   iv. In one example, Ry may be calculated directly                depending on ySb′, and/or a motion vector, and/or a                resampling ratio. In other words, the two steps of                derivation on Ry′ and Ry are combined into a one-step                calculation.            -   v. Whether to and/or how to use the top position (e.g.                conf_win_top_offset as defined in VVC) of the                conformance window of the current picture and/or the                reference picture may depend on the color components                and/or color formats.                -   1) For example, conf_win_top_offset may be revised                    as                    conf_win_top_offset=conf_win_top_offset*SubHeightC,                    wherein SubHeightC defines the vertical sampling                    step of a color component. E.g., SubHeightC is equal                    to 1 for the luma component. SubHeightC is equal to                    2 for a chroma component when the color format is                    4:2:0.                -   2) For example, conf_win_top_offset may be revised                    as                    conf_win_top_offset=conf_win_top_offset/SubHeightC,                    wherein SubHeightC defines the vertical sampling                    step of a color component. E.g., SubHeightC is equal                    to 1 for the luma component. SubHeightC is equal to                    2 for a chroma component when the color format is                    4:2:0.    -   28. It is proposed that the integer part of the horizontal        coordinate of a reference sample may be clipped to [minW, maxW].        Suppose the width and height of the conformance window of the        reference picture are denoted as W and H, respectively. The        width and height of the conformance window of a reference        picture are denoted as W′ and H′. The top-left position of the        conformance window in the reference picture are denoted as (X0,        Y0).        -   a. In one example, minW is equal to 0.        -   b. In one example, minW is equal to X0.        -   c. In one example, maxW is equal to W−1.        -   d. In one example, maxW is equal to W′−1.        -   e. In one example, maxW is equal to X0+W′−1.        -   f. In one example, minW and/or maxW may be modified based on            color format and/or color component.            -   i. For example, minW is modified to be minW*SubC.            -   ii. For example, minW is modified to be minW/SubC.            -   iii. For example, maxW is modified to be maxW*SubC.            -   iv. For example, maxW is modified to be maxW/SubC.            -   v. In one example, SubC is equal to 1 for the luma                component.            -   vi. In one example, SubC is equal to 2 for a chroma                component when the color format is 4:2:0.            -   vii. In one example, SubC is equal to 2 for a chroma                component when the color format is 4:2:2.            -   viii. In one example, SubC is equal to 1 for a chroma                component when the color format is 4:4:4.        -   g. In one example, the whether to and/or how to do the            clipping may depend on the dimensions of the current picture            (or the conformance window in it) and the dimensions of the            reference picture (or the conformance window in it).            -   i. In one example, the clipping is done only when the                dimensions of the current picture (or the conformance                window in it) and the dimenstions of the reference                picture (or the conformance window in it) are different.    -   29. It is proposed that the integer part of the vertical        coordinate of a reference sample may be clipped to [minH, maxH].        Suppose the width and height of the conformance window of the        reference picture are denoted as W and H, respectively. The        width and height of the conformance window of a reference        picture are denoted as W′ and H′. The top-left position of the        conformance window in the reference picture are denoted as (X0,        Y0).        -   a. In one example, minH is equal to 0.        -   b. In one example, minH is equal to Y0.        -   c. In one example, maxH is equal to H−1.        -   d. In one example, maxH is equal to H′−1.        -   e. In one example, maxH is equal to Y0+H′−1.        -   f. In one example, minH and/or maxH may be modified based on            color format and/or color component.            -   i. For example, minH is modified to be minH*SubC.            -   ii. For example, minH is modified to be minH/SubC.            -   iii. For example, maxH is modified to be maxH*SubC.            -   iv. For example, maxH is modified to be maxH/SubC.            -   v. In one example, SubC is equal to 1 for the luma                component.            -   vi. In one example, SubC is equal to 2 for a chroma                component when the color format is 4:2:0.            -   vii. In one example, SubC is equal to 1 for a chroma                component when the color format is 4:2:2.            -   viii. In one example, SubC is equal to 1 for a chroma                component when the color format is 4:4:4.        -   g. In one example, the whether to and/or how to do the            clippling may depend on the dimenstions of the current            picture (or the conformance window in it) and the            dimenstions of the reference picture (or the conformance            window in it).            -   i. In one exmaple, the clipping is done only when the                dimenstions of the current picture (or the conformance                window in it) and the dimenstions of the reference                picture (or the conformance window in it) are different.

In the following discussion, a first syntax element is asserted to be“corresponding” to a second syntax element, if the two syntax elementshave an equivalent functionality but may be signaled at different videounit (e.g. VPS/SPS/PPS/slice header/picture header etc.)

-   -   30. It is proposed that a syntax element may be signaled in a        first video unit (e.g. picture header or PPS) and no        corresponding syntax element is signaled in a second video unit        at a higher level (such as SPS) or a lower level (such as slice        header).        -   a. Alternatively, a first syntax element may be signaled in            the first video unit (e.g. picture header or PPS) and a            corresponding second syntax element may be signaled in a            second video unit at a lower level (such as slice header).            -   i. Alternatively, an indicator may be signaled in the                second video unit to inform whether the second syntax                element is signaled thereafter.            -   ii. In one example, the slice associated with the second                video unit (such as slice header) may follow the                indication of the second syntax element instead of the                first one if the second one is signaled.            -   iii. An indicator associated with the first syntax                element may be signaled in the first video unit to                inform whether the second syntax element is signaled in                any slice (or other video unit) associated with the                first video unit.        -   b. Alternatively, a first syntax element may be signaled in            a first video unit at a higher level (such as VPS/SPS/PPS),            and a corresponding second syntax element may be signaled in            the second video unit (such as picture header).            -   i. Alternatively, an indicator may be signaled to inform                whether the second syntax element is signaled                thereafter.            -   ii. In one example, the picture (which may be                partitioned into slices) associated with the second                video unit may follow the indication of the second                syntax element instead of the first one if the second                one is signaled.        -   c. A first syntax element in the picture header may have an            equivalent functionality as a second syntax element in the            slice header as specified in section 2.6 (such as but            limited to slice_temporal_mvp_enabled_flag, cabac_init_flag,            six_minus_max_num_merge_cand,            five_minus_max_num_subblock_merge_cand,            slice_fpel_mmvd_enabled_flag, slice_disable_bdof_dmvr_flag,            max_num_merge_cand_minus_max_num_triangle_cand,            slice_fpel_mmvd_enabled_flag,            slice_six_minus_max_num_ibc_merge_cand,            slice_joint_cbcr_sign_flag, slice_qp_delta, . . . ) but            control all slices of the picture.        -   d. A first syntax element in SPS as specified in section 2.6            may have an equivalent functionality as a second syntax            element in the picture header (such as but limited to            sps_bdof_dmvr_slice_present_flag, sps_mmvd_enabled_flag,            sps_isp_enabled_flag, sps_mrl_enabled_flag,            sps_mip_enabled_flag, sps_cclm_enabled_flag,            sps_mts_enabled_flag . . . ) but control only the associated            picture (which may be partitioned into slices).        -   e. A first syntax element in PPS as specified in section 2.7            may have an equivalent functionality as a second syntax            element in the picture header (such as but limited to            entropy_coding_sync_enabled_flag,            entry_point_offsets_present_flag, cabac_init_present_flag,            rpl1_idx_present_flag . . . ) but control only the            associated picture (which may be partitioned into slices).    -   31. Syntax elements signaled in the picture header are decoupled        from other syntax elements signaled or derived in the        SPS/VPS/DPS.    -   32. Indications of enabling/disabling of DMVR and BDOF may be        signaled separately in picture header, instead of being        controlled by the same flag (e.g, pic_disable_bdof_dmvr_flag).    -   33. Indications of enabling/disabling of PROF/cross-component        ALF/inter prediction with geometric partitioning (GEO) may be        signaled in picture headers.        -   a. Alternatively, the indication of enabling/disabling PROF            in picture header may be conditionally signaled according to            the PROF enabling flag in SPS.        -   b. Alternatively, the indication of enabling/disabling            cross-component ALF (CCALF) in picture header may be            conditionally signaled according to the CCALF enabling flag            in SPS.        -   c. Alternatively, the indication of enabling/disabling GEO            in picture header may be conditionally signaled according to            the GEO enabling flag in SPS.        -   d. Alternatively, furthermore, indications of            enabling/disabling of PROF/cross-component ALF/inter            prediction with geometric partitioning (GEO) in slice            headers may be conditionally signaled according to those            syntax elements signaled in picture header instead of SPS.    -   34. Indications of prediction types of slices/bricks/tiles (or        other video units smaller than a picture) in the same picture        may be signaled in picture header.        -   a. In one example, an indication of whether all            slices/bricks/tiles (or other video units smaller than a            picture) are all intra-coded (e.g., all I slices) may be            signaled in the picture header.            -   i. Alternatively, furthermore, the slice types may not                be signaled in slice header if the indication tells all                slices within the picture are I slices.        -   b. Alternatively, an indication of whether at least one of            slices/bricks/tiles (or other video units smaller than a            picture) is not intra-coded (e.g., at least one non-I            slices) may be signaled in the picture header.        -   c. Alternatively, an indication of whether all            slices/bricks/tiles (or other video units smaller than a            picture) are all with the same prediction types (e.g., I/P/B            slices) may be signaled in the picture header.            -   i. Alternatively, furthermore, the slice types may not                be signaled in slice header.            -   ii. Alternatively, furthermore, indication of tools                which are allowed for specific prediction types (e.g,                DMVR/BDOF/TPM/GEO are only allowed for B slices; dual                tree is only allowed for I slices) may be conditionally                signaled according to the indication of prediction                types.        -   d. Alternatively, furthermore, signaling of indications of            enabling/disabling tools may depend on the indications of            prediction types mentioned in above sub-bullets.            -   i. Alternatively, furthermore, indications of                enabling/disabling tools may be derived according to the                indications of prediction types mentioned in above                sub-bullets.    -   35. In this disclosure (bullet 1-bullet 29), the term        “conformance window” may be replaced by other terms such as        “scaling window”. A scaling window may be signaled differently        to the conformance window and is used to derive the scaling        ratio and/or top-left offset used to derive the reference sample        position for RPR.        -   a. In one example, the scaling window may be constrained by            the conformance window. For example, in a conformance            bit-stream, the scaling window must be contained by the            conformance window.    -   36. Whether and/or how to signal the allowed max block size for        transform-skip-coded blocks may depend on the max block size for        transform-coded blocks.        -   a. Alternatively, the max block size for            transform-skip-coded blocks cannot be larger than max block            size for transform-coded blocks in a conformance bitstream.    -   37. Whether and how to signal the indication of enabling Joint        Cb-Cr Residue (JCCR) coding (such as        sps_joint_cbcr_enabled_flag) may depend the color format (such        as 4:0:0, 4:2:0 etc.)        -   a. For example, the indication of enabling Joint Cb-Cr            Residue (JCCR) may not be signaled if the color format is            4:0:0. An exemplary syntax design is as below:

 sps_joint_cbcr_enabled_flag u(1)

Downsampling Filter Type for Chroma Blending Mask Generation in TPM/GEO

-   -   38. The type of downsampling filter used for blending weights        derivation for chroma samples may be signalled at video unit        level (such as SPS/VPS/PPS/Picture header/Subpicture/Slice/Slice        header/Tile/Brick/CTU/VPDU level).        -   a. In one example, a high level flag may be signaled to            switch between different chroma format types of content.            -   i. In one example, a high level flag may be signaled to                switch between chroma format type 0 and chroma format                type 2.            -   ii. In one example, a flag may be signaled for                specifying whether the top-left downsampled luma weights                in TPM/GEO prediction mode is collocated with the                top-left luma weights (e.g., chroma sample location type                0).            -   iii. In one example, a flag may be signaled for                specifying whether the top-left downsampled luma sample                in TPM/GEO prediction mode is horizontally co-sited with                the top-left luma sample but vertically shifted by 0.5                units of luma samples relatively to the top-left luma                sample (e.g., chroma sample location type 2).        -   b. In one example, the type of downsampling filter may be            signaled for 4:2:0 chroma format and/or 4:2:2 chroma format.        -   c. In one example, a flag may be signaled for specifying the            type of chroma downsampling filter used for TPM/GEO            prediction.            -   i. In one example, the flag may be signaled for whether                to use downsampling filter A or downsampling filter B                for the chroma weights derivation in TPM/GEO prediction                mode.    -   39. The type of downsampling filter used for blending weights        derivation for chroma samples may be derived at video unit level        (such as SPS/VPS/PPS/Picture header/Subpicture/Slice/Slice        header/Tile/Brick/CTU/VPDU level).        -   a. In one example, a look up table may be defined to specify            the correspondence relationship between the chroma            subsampling filter type and the chroma format types of            content.    -   40. A specified downsampling filter may be used for TPM/GEO        prediction mode in case of different chroma sample location        type.        -   a. In one example, chroma weights of TPM/GEO may be            subsampled from the collocated top-left luma weights in case            of a certain chroma sample location type (e.g., chroma            sample location type 0).        -   b. In one example, in case of a certain chroma sample            location type (e.g., chroma sample location type 0 or 2), a            specified X-tap filter (X is a constant such as X=6 or 5)            may be used for chroma weights subsampling in TPM/GEO            prediction mode.    -   41. In a video unit (e.g. SPS,PPS, picture header, slice header        etc.), a first syntax element (such as a flag) may be signaled        to indicate whether Multiple Transform Selection (MTS) is        disabled for all blocks (slices/pictures).        -   a. A second syntax element indicating how to apply MTS (such            as enable MTS/disable MTS/implicit MTS/explicit MTS) on            intra-coding blocks (slices/pictures) is signaled            conditionally on the first syntax element. For example, the            second syntax element is signaled only when the first syntax            element indicates that MTS is not disabled for all blocks            (slices/pictures).        -   b. A third syntax element indicating how to apply MTS (such            as enable MTS/disable MTS/implicit MTS/explicit MTS) on            inter-coding blocks (slices/pictures) is signaled            conditionally on the first syntax element. For example, the            third syntax element is signaled only when the first syntax            element indicates that MTS is not disabled for all blocks            (slices/pictures).        -   c. An exemplary syntax design is as below

...  enable_mts_flag  if( enable_mts_flag){   mts_control_intra  mts_control_inter } ...

-   -   d. The third syntax element may be signaled conditionally on        whether Sub-Block Transform (SBT) is applied or not. An        exemplary syntax design is as below

...  if (sps_sbt_enabled_flag)   mts_control_inter ...

-   -   e. An exemplary syntax design is as below

—

—

Determination of Usage of a Coding Tool X

-   -   42. The determination of whether to and/or how to enable a        coding tool X may depend on the width and/height of a        considering picture of one or multiple reference pictures and/or        current picture.        -   a. The width and/height of a considering picture of one or            multiple reference pictures and/or current picture may be            modified to make the determination.        -   b. The considering picture may be defined by the conformance            window or the scaling window.            -   i. The considering picture may be the whole picture.        -   c. In one example, whether to and/or how to enable a coding            tool X may depend on the width of a picture minus one or            multiple offsets in the horizontal and/or height of a            picture minus an offset in the vertical direction.            -   i. In one example, the horizontal offset may be defined                as the scaling_win_left_offset.            -   ii. In one example, the vertical offset may be defined                as the scaling_win_top_offset.            -   iii. In one example, the horizontal offset may be                defined as                (scaling_win_right_offset+scaling_win_left_offset).            -   iv. In one example, the vertical offset may be defined                as (scaling_win_bottom_offset+scaling_win_top_offset).            -   v. In one example, the horizontal offset may be defined                as                SubWidthC*(scaling_win_right_offset+scaling_win_left_offset).            -   vi. In one example, the vertical offset may be defined                as                SubHeightC*(scaling_win_bottom_offset+scaling_win_top_offset).        -   d. In one example, if at least one of the two considering            reference pictures have different resolution (either width            or height) with current picture, the coding tool X is            disabled.            -   i. Alternatively, if at least one of the two output                reference pictures have a dimension (either width or                height) larger than that of the current picture, the                coding tool X is disabled.        -   e. In one example, if one considering reference picture for            a reference picture list L has different resolution with            current picture, the coding tool X is disabled for the            reference picture list L.            -   i. Alternatively, if one considering reference picture                for a reference picture list L has a dimension (either                width or height) larger than that of the current                picture, the coding tool X is disabled for the reference                picture list L.        -   f. In one example, if two considering reference pictures of            two reference picture lists are with different resolutions,            the coding tool may be disabled.            -   i. Alternatively, the indications of the coding tool may                be conditionally signalled according to resolutions.            -   ii. Alternatively, signalling of the indications of the                coding tool may be skipped.        -   g. In one example, if two considering reference pictures of            two merge candidates utilized to derive a first pairwise            merge candidate for at least one reference picture list, the            coding tool may be disabled, e.g., the first pairwise merge            candidate is marked as unavailable.            -   i. Alternatively, if two considering reference pictures                of two merge candidates utilized to derive a first                pairwise merge candidate for both reference picture                lists, the coding tool may be disabled, e.g., the first                pairwise merge candidate is marked as unavailable.        -   h. In one example, the decoding process of the coding tool            may be modified with the consideration of picture dimension.            -   i. In one example, the derivation of MVD for another                reference picture list (e.g., list 1) in SMVD may be                based on the resolution differences (e.g., scaling                factors) of at least one of the two target SMVD                reference pictures.            -   ii. In one example, the derivation of pairwise merge                candidate may be based on the resolution differences                (e.g., scaling factors) of at least one of the two                reference pictures associated with two reference                pictures, e.g., linear weighted average may be applied                instead of equal weights.        -   i. In one example, X may be:            -   i. DMVR/BDOF/PROF/SMVD/MMVD/other coding tools that                refine motion/prediction at the decoder side            -   ii. TMVP/other coding tools rely on temporal motion                information            -   iii. MTS or other transform coding tools            -   iv. CC-ALF            -   v. TPM            -   vi. GEO            -   vii. Switchable interpolation filter (e.g., alternative                interpolation filter for half-pel motion compensation)            -   viii. The blending process in TPM/GEO/other coding tools                that split one block into multiple partitions.            -   ix. A coding tool that replies on the stored information                in a picture different from current picture            -   x. Pairwise merge candidate (when certain conditions                related to resolution are not satisfied, pairwise merge                candidate is not generated)            -   xi. Bi-prediction with CU-level Weights (BCW).            -   xii. Weighted prediction.            -   xiii. Affine prediction            -   xiv. Adaptive Motion Vector Resolution (AMVR)    -   43. Whether to and/or how to signal the usage of a coding tool        may depend on the width and/height of an considering picture of        one or multiple reference pictures and/or current picture.        -   a. The width and/height of a considering picture of one or            multiple reference pictures and/or current picture may be            modified to make the determination.        -   b. The considering picture may be defined by the conformance            window or the scaling window as defined in JVET-P0590.            -   xv. The considering picture may be the whole picture.        -   c. In one example, X may be the adaptive motion vector            resolution (ΔMVR).        -   d. In one example, X may be the merge with MV differences            (MMVD) method.            -   xvi. In one example, the construction of symmetric                motion vector difference reference indices may depend on                the picture resolutions/indications of RPR cases for                different reference pictures.        -   e. In one example, X may be the symmetric MVD (SMVD) method.        -   f. In one example, X may be the QT/BT/TT or other            partitioning types.        -   g. In one example, X may be Bi-prediction with CU-level            Weights (BCW).        -   h. In one example, X may be Weighted prediction.        -   i. In one example, X may be Affine prediction.        -   j. In one example, whether to signal the indication of usage            of half-pel motion vector precision/switchable interpolation            filter may depend on the resolution information/whether RPR            is enabled for current block.        -   k. In one example, the signalling of amvr_precision_idx may            depend on the resolution information/whether RPR is enabled            for current block.        -   l. In one example, the signalling of            sym_mvd_flag/mmvd_merge_flag may depend on the resolution            information/whether RPR is enabled for current block.        -   m. A conformance bitstream shall satisfy that the 1/2-pel MV            and/or MVD precision (e.g., the alternative interpolation            filter/switchable interpolation filter) is disallowed when            the width and/height of a considering picture of one or            multiple reference pictures is different from that of            current output picture.    -   44. It is proposed that AMVR with 1/2-pel MV and/or MVD        precision (or alternative interpolation filter/switchable        interpolation filter) may be still enabled for a block in RPR.        -   a. Alternatively, furthermore, a different interpolation            filter may be applied for blocks with 1/2-pel or other            precisions.    -   45. The condition check of same/different resolutions in above        bullets may be replaced by adding a flag for a reference picture        and checking the flags associated with reference pictures.        -   a. In one example, the process of setting the flag to be            true or false (e.g., to indicate whether the reference            picture is RPR case or non-RPR case) may be invoked during            the reference picture list construction process.            -   xvii. For example, the following may be applied:                -   fRefWidth is set equal to PicOutputWidthL of the                    reference picture RefPicList[i][j] in luma samples,                    where PicOutputWidthL represents the width of the                    considering picture of the reference picture.                -   fRefWidth is set equal to PicOutputHeightL of the                    reference picture RefPicList[i][j] in luma samples,                    where PicOutputHeightL represents the height of the                    considering picture of the reference picture.

RefPicScale[i][j][0]=((fRefWidth<<14)+(PicOutputWidthL>>1))/PicOutputWidthL,

-   -   -   -   -   where                -   PicOutputWidthL represents the width of the                    considering picture of the current picture.

RefPicScale[i][j][1]=((fRefHeight<<14)+(PicOutputHeightL>>1))/PicOutputHeightL,

-   -   -   -   -   where PicOutputWidthL represents the height of the                    considering picture of the current picture

RefPicIsScaled[i][j]=(RefPicScale[i][j][0]!=(1<<14))∥(RefPicScale[i][j][1]!=(1<<14))

-   -   -   -   -   wherein RefPicList[i][j] represents the j-th                    reference picture in reference picture list i.

        -   b. In one example, when either RefPicIsScaled[0][refIdxL0]            is unequal to 0 or RefPicIsScaled[1][refIdxL1] is unequal to            0, a coding tool X (e.g.,            DMVR/BDOF/SMVD/MMVD/SMVD/PROF/those mentioned in above            bullets) may be disabled.

        -   c. In one example, when both RefPicIsScaled[0][refIdxL0] and            RefPicIsScaled[1][refIdxL1] are unequal to 0, a coding tool            X (e.g., DMVR/BDOF/SMVD/MMVD/SMVD/PROF/those mentioned in            above bullets) may be disabled.

        -   d. In one example, when RefPicIsScaled[0][refIdxL0] is            unequal to 0, a coding tool X (e.g., PROF or those mentioned            in above bullets) may be disabled for reference picture list            0.

        -   e. In one example, when RefPicIsScaled[1][refIdxL1] is            unequal to 0, a coding tool X (e.g., PROF or those mentioned            in above bullets) may be disabled for reference picture list            1.

    -   46. The SAD and/or threshold used by BDOF/DMVR may be dependent        on the bit-depth.        -   f. In one example, the calculated SAD value may be firstly            shifted by a function of bit-depth before being utilized to            be compared to a threshold.        -   g. In one example, the calculated SAD value may be directly            compared with a modified threshold which may depend on a            function of bit-depth.

5. Additional Embodiments

In the following, text changes are shown in underlined bold italicizedfont.

5.1. Embodiment of Constrains on the Conformance Window

conf_win_left_offset, conf_win_right_offset, conf_win_top_offset, andconf_win_bottom_offset specify the samples of the pictures in the CVSthat are output from the decoding process, in terms of a rectangularregion specified in picture coordinates for output. Whenconformance_window_flag is equal to 0, the values ofconf_win_left_offset, conf_win_right_offset, conf_win_top_offset, andconf_win_bottom_offset are inferred to be equal to 0. The conformancecropping window contains the luma samples with horizontal picturecoordinates from SubWidthC*conf_win_left_offset topic_width_in_luma_samples−(SubWidthC*conf_win_right_offset+1) andvertical picture coordinates from SubHeightC*conf_win_top_offset topic_height_in_luma_samples−(SubHeightC*conf_win_bottom_offset+1),inclusive.The value of SubWidthC*(conf_win_left_offset+conf_win_right_offset)shall be less than pic_width_in_luma_samples, and the value ofSubHeightC*(conf_win_top_offset+conf_win_bottom_offset) shall be lessthan pic_height_in_luma_samples.The variables PicOutputWidthL and PicOutputHeightL are derived asfollows:

PicOutputWidthL=pic_width_in_luma_samples−SubWidthC*(conf_win_right_offset+conf_win_left_offset)  (7-43)

PicOutputHeightL=pic_height_in_pic_size_units−SubHeightC*(conf_win_bottom_offset+conf_win_top_offset)  (7-44)

When ChromaArrayType is not equal to 0, the corresponding specifiedsamples of the two chroma arrays are the samples having picturecoordinates (x/SubWidthC, y/SubHeightC), where (x, y) are the picturecoordinates of the specified luma samples.

-   -   

    -   

    -   

    -   

5.2. Embodiment 1 of Reference Sample Position Derivation

8.5.6.3.1 General

. . .The variable fRefWidth is set equal to the PicOutputWidthL of thereference picture in luma samples.The variable fRefHeight is set equal to PicOutputHeightL of thereference picture in luma samples.

The motion vector mvLX is set equal to (refMvLX−mvOffset).

-   -   If cIdx is equal to 0, the following applies:        -   The scaling factors and their fixed-point representations            are defined as

hori_scale_fp=((fRefWidth<<14)+(PicOutputWidthL>>1))/PicOutputWidthL  (8-753)

vert_scale_fp=((fRefHeight<<14)+(PicOutputHeightL>>1))/PicOutputHeightL  (8-754)

-   -   -   Let (xIntL, yIntL) be a luma location given in full-sample            units and (xFracL, yFracL) be an offset given in 1/16-sample            units. These variables are used only in this clause for            specifying fractional-sample locations inside the reference            sample arrays refPicLX.        -   The top-left coordinate of the bounding block for reference            sample padding (xSbInt_(L), ySbInt_(L)) is set equal to            (xSb+(mvLX[0]>>4), ySb+(mvLX[1]>>4)).        -   For each luma sample location (x_(L)=0 . . .            sbWidth−1+brdExtSize, y_(L)=0 . . . sbHeight−1+brdExtSize)            inside the prediction luma sample array predSamplesLX, the            corresponding prediction luma sample value            predSamplesLX[x_(L)][y_(L)] is derived as follows:            -   Let (refxSb_(L), refySb_(L)) and (refx_(L), refy_(L)) be                luma locations pointed to by a motion vector                (refMvLX[0], refMvLX[1]) given in 1/16-sample units. The                variables refxSb_(L), refx_(L), refySb_(L), and refy_(L)                are derived as follows:

refxSb_(L)=(((

<<4)+refMvLX[0])*hori_scale_fp  (8-755)

refx_(L)=((Sign(refxSb)*((Abs(refxSb)+128)>>8)+x_(L)*((hori_scale_fp+8)>>4))+32)>>6  (8-756)

refySb_(L)=((

<<4)+refMvLX[1])*vert_scale_fp  (8-757)

refy_(L)=((Sign(refySb)*((Abs(refySb)+128)>>8)+yL*((vert_scale_fp+8)>>4))+32)>>6  (8-758)

-   -   -   -   

            -   

            -   The variables xInt_(L), yInt_(L), xFrac_(L) and                yFrac_(L) are derived as follows:

xInt_(L)=refx_(L)>>4  (8-759)

yInt_(L)=refy_(L)>>4  (8-760)

xFrac_(L)=refx_(L)&15  (8-761)

yFrac_(L)=refy_(L)&15  (8-762)

-   -   -   If bdofFlag is equal to TRUE or            (sps_affine_prof_enabled_flag is equal to TRUE and            inter_affine_flag[xSb][ySb] is equal to TRUE), and one or            more of the following conditions are true, the prediction            luma sample value predSamplesLX[x_(L)][y_(L)] is derived by            invoking the luma integer sample fetching process as            specified in clause 8.5.6.3.3 with            (xInt_(L)+(xFrac_(L)>>3)−1), yInt_(L)+(yFrac_(L)>>3)−1) and            refPicLX as inputs.            -   x_(L) is equal to 0.            -   x_(L) is equal to sbWidth+1.            -   y_(L) is equal to 0.            -   y_(L) is equal to sbHeight+1.        -   Otherwise, the prediction luma sample value            predSamplesLX[xL][yL] is derived by invoking the luma sample            8-tap interpolation filtering process as specified in clause            8.5.6.3.2 with (xIntL−(brdExtSize>0?1:0),            yIntL−(brdExtSize>0?1:0)), (xFracL, yFracL), (xSbInt_(L),            ySbInt_(L)), refPicLX, hpelIfIdx, sbWidth, sbHeight and            (xSb, ySb) as inputs.

    -   Otherwise (cIdx is not equal to 0), the following applies:        -   Let (xIntC, yIntC) be a chroma location given in full-sample            units and (xFracC, yFracC) be an offset given in 1/32 sample            units. These variables are used only in this clause for            specifying general fractional-sample locations inside the            reference sample arrays refPicLX.        -   The top-left coordinate of the bounding block for reference            sample padding (xSbIntC, ySbIntC) is set equal to            ((xSb/SubWidthC)+(mvLX[0]>>5),            (ySb/SubHeightC)+(mvLX[1]>>5)).        -   For each chroma sample location (xC=0 . . . sbWidth−1, yC=0            . . . sbHeight−1) inside the prediction chroma sample arrays            predSamplesLX, the corresponding prediction chroma sample            value predSamplesLX[xC][yC] is derived as follows:            -   Let (refxSb_(C), refySb_(C)) and (refx_(C), refy_(C)) be                chroma locations pointed to by a motion vector (mvLX[0],                mvLX[1]) given in 1/32-sample units. The variables                refxSb_(C), refySb_(C), refx_(C) and refy_(C) are                derived as follows:

refxSb_(C)=((

/SubWidthC<<5)+mvLX[0])*hori_scale_fp   (8-763)

refx_(C)=((Sign(refxSb_(C))*((Abs(refxSb_(C))+256)>>9)+xC*((hori_scale_fp+8)>>4))+16)>>5  (8-764)

refySb_(C)=((

/SubHeightC<<5)+mvLX[1])*vert_scale_fp   (8-765)

refy_(C)=((Sign(refySb_(C))*((Abs(refySb_(C))+256)>>9)+yC*((vert_scale_fp+8)>>4))+16)>>5  (8-766)

-   -   -   -   

            -   

            -   The variables xInt_(C), yInt_(C), xFrac_(C) and                yFrac_(C) are derived as follows:

xInt_(C)=refx_(C)>>5  (8-767)

yInt_(C)=refy_(C)>>5  (8-768)

xFrac_(C)=refy_(C)&31  (8-769)

yFrac_(C)=refy_(C)&31  (8-770)

5.3. Embodiment 2 of Reference Sample Position Derivation

8.5.6.3.1 General

. . .The variable fRefWidth is set equal to the PicOutputWidthL of thereference picture in luma samples.The variable fRefHeight is set equal to PicOutputHeightL of thereference picture in luma samples.

The motion vector mvLX is set equal to (refMvLX−mvOffset).

-   -   If cIdx is equal to 0, the following applies:        -   The scaling factors and their fixed-point representations            are defined as

hori_scale_fp=((fRefWidth<<14)+(PicOutputWidthL>>1))/PicOutputWidthL  (8-753)

vert_scale_fp=((fRefHeight<<14)+(PicOutputHeightL>>1))/PicOutputHeightL  (8-754)

-   -   -   Let (xIntL, yIntL) be a luma location given in full-sample            units and (xFracL, yFracL) be an offset given in 1/16-sample            units. These variables are used only in this clause for            specifying fractional-sample locations inside the reference            sample arrays refPicLX.        -   The top-left coordinate of the bounding block for reference            sample padding (xSbInt_(L), ySbInt_(L)) is set equal to            (xSb+(mvLX[0]>>4), ySb+(mvLX[1]>>4)).        -   For each luma sample location (x_(L)=0 . . .            sbWidth−1+brdExtSize, y_(L)=0 . . . sbHeight−1+brdExtSize)            inside the prediction luma sample array predSamplesLX, the            corresponding prediction luma sample value            predSamplesLX[x_(L)][y_(L)] is derived as follows:            -   Let (refxSb_(L), refySb_(L)) and (refx_(L), refy_(L)) be                luma locations pointed to by a motion vector                (refMvLX[0], refMvLX[1]) given in 1/16-sample units. The                variables refxSb_(L), refx_(L), refySb_(L), and refy_(L)                are derived as follows:

refxSb_(L)=((

<<4)+refMvLX[0])*hori_scale_fp  (8-755)

refx_(L)=((Sign(refxSb)*((Abs(refxSb)+128)>>8)+x_(L)*((hori_scale_fp+8)>>4))

+32)>>6  (8-756)

refySb_(L)=((

<<4)+refMvLX[1])*vert_scale_fp  (8-757)

refy_(L)=((Sign(refySb)*((Abs(refySb)+128)>>8)+yL*((vert_scale_fp+8)>>4))

+32)>>6  (8-758)

-   -   -   -   The variables xInt_(L), yInt_(L), xFrac_(L) and                yFrac_(L) are derived as follows:

xInt_(L)=refx_(L)>>4  (8-759)

yInt_(L)=refy_(L)>>4  (8-760)

xFrac_(L)=refx_(L)&15  (8-761)

yFrac_(L)=refy_(L)&15  (8-762)

-   -   -   If bdofFlag is equal to TRUE or            (sps_affine_prof_enabled_flag is equal to TRUE and            inter_affine_flag[xSb][ySb] is equal to TRUE), and one or            more of the following conditions are true, the prediction            luma sample value predSamplesLX[x_(L)][y_(L)] is derived by            invoking the luma integer sample fetching process as            specified in clause 8.5.6.3.3 with            (xInt_(L)+(xFrac_(L)>>3)−1), yInt_(L)+(yFrac_(L)>>3)−1) and            refPicLX as inputs.            -   x_(L) is equal to 0.            -   x_(L) is equal to sbWidth+1.            -   y_(L) is equal to 0.            -   y_(L) is equal to sbHeight+1.        -   Otherwise, the prediction luma sample value            predSamplesLX[x_(L)][y_(L)] is derived by invoking the luma            sample 8-tap interpolation filtering process as specified in            clause 8.5.6.3.2 with (xInt_(L)−(brdExtSize>0?1:0),            yInt_(L)−(brdExtSize>0?1:0)), (xFracL, yFracL), (xSbInt_(L),            ySbInt_(L)), refPicLX, hpelIfIdx, sbWidth, sbHeight and            (xSb, ySb) as inputs.

    -   Otherwise (cIdx is not equal to 0), the following applies:        -   Let (xIntC, yIntC) be a chroma location given in full-sample            units and (xFracC, yFracC) be an offset given in 1/32 sample            units. These variables are used only in this clause for            specifying general fractional-sample locations inside the            reference sample arrays refPicLX.        -   The top-left coordinate of the bounding block for reference            sample padding (xSbIntC, ySbIntC) is set equal to            ((xSb/SubWidthC)+(mvLX[0]>>5),            (ySb/SubHeightC)+(mvLX[1]>>5)).        -   For each chroma sample location (xC=0 . . . sbWidth−1, yC=0            . . . sbHeight−1) inside the prediction chroma sample arrays            predSamplesLX, the corresponding prediction chroma sample            value predSamplesLX[xC][yC] is derived as follows:            -   Let (refxSb_(C), refySb_(C)) and (refx_(C), refy_(C)) be                chroma locations pointed to by a motion vector (mvLX[0],                mvLX[1]) given in 1/32-sample units. The variables                refxSb_(C), refySb_(C), refx_(C) and refy_(C) are                derived as follows:

refxSb_(C)=(

/SubWidthC<<5)+mvLX[0])*hori_scale_fp   (8-763)

refx_(C)=((Sign(refxSb_(C))*((Abs(refxSb_(C))+256)>>9)+xC*((hori_scale_fp+8)>>4))+16)>>5  (8-764)

refySb_(C)=((

/SubHeightC<<5)+mvLX[1])*vert_scale_fp   (8-765)

refy_(C)=((Sign(refySb_(C))*((Abs(refySb_(C))+256)>>9)+yC*((vert_scale_fp+8)>>4))+16)>>5  (8-766)

-   -   -   -   

            -   

            -   The variables xInt_(C), yInt_(C), xFrac_(C) and                yFrac_(C) are derived as follows:

xInt_(C)=refx_(C)>>5  (8-767)

yInt_(C)=refy_(C)>>5  (8-768)

xFrac_(C)=refy_(C)&31  (8-769)

yFrac_(C)=refy_(C)&31  (8-770)

5.4. Embodiment 3 of Reference Sample Position Derivation

8.5.6.3.1 General

. . .The variable fRefWidth is set equal to the PicOutputWidthL of thereference picture in luma samples.The variable fRefHeight is set equal to PicOutputHeightL of thereference picture in luma samples.

The motion vector mvLX is set equal to (refMvLX−mvOffset).

-   -   If cIdx is equal to 0, the following applies:        -   The scaling factors and their fixed-point representations            are defined as

hori_scale_fp=((fRefWidth<<14)+(PicOutputWidthL>>1))/PicOutputWidthL  (8-753)

vert_scale_fp=((fRefHeight<<14)+(PicOutputHeightL>>1))/PicOutputHeightL  (8-754)

-   -   -   Let (xIntL, yIntL) be a luma location given in full-sample            units and (xFracL, yFracL) be an offset given in 1/16-sample            units. These variables are used only in this clause for            specifying fractional-sample locations inside the reference            sample arrays refPicLX.        -   The top-left coordinate of the bounding block for reference            sample padding (xSbInt_(L), ySbInt_(L)) is set equal to            (xSb+(mvLX[0]>>4), ySb+(mvLX[1]>>4)).        -   For each luma sample location (x_(L)=0 . . .            sbWidth−1+brdExtSize, y_(L)=0 . . . sbHeight−1+brdExtSize)            inside the prediction luma sample array predSamplesLX, the            corresponding prediction luma sample value            predSamplesLX[x_(L)][y_(L)] is derived as follows:            -   Let (refxSb_(L), refySb_(L)) and (refx_(L), refy_(L)) be                luma locations pointed to by a motion vector                (refMvLX[0], refMvLX[1]) given in 1/16-sample units. The                variables refxSb_(L), refx_(L), refySb_(L), and refy_(L)                are derived as follows:

refxSb_(L)=((

<<4)+refMvLX[0])*hori_scale_fp  (8-755)

refx_(L)=((Sign(refxSb)*((Abs(refxSb)+128)>>8)+x_(L)*((hori_scale_fp+8)>>4))

32)>>6  (8-756)

refySb_(L)=((

<<4)+refMvLX[1])*vert_scale_fp  (8-757)

refy_(L)=((Sign(refySb)*((Abs(refySb)+128)>>8)+yL*((vert_scale_fp+8)>>4))

+32)>>6  (8-758)

-   -   -   -   The variables xInt_(L), yInt_(L), xFrac_(L) and                yFrac_(L) are derived as follows:

xInt_(L)=refx_(L)>>4  (8-759)

yInt_(L)=refy_(L)>>4  (8-760)

xFrac_(L)=refx_(L)&15  (8-761)

yFrac_(L)=refy_(L)&15  (8-762)

-   -   -   If bdofFlag is equal to TRUE or            (sps_affine_prof_enabled_flag is equal to TRUE and            inter_affine_flag[xSb ySb] is equal to TRUE), and one or            more of the following conditions are true, the prediction            luma sample value predSamplesLX[x_(L)][y_(L)] is derived by            invoking the luma integer sample fetching process as            specified in clause 8.5.6.3.3 with            (xInt_(L)+(xFrac_(L)>>3)−1), yInt_(L)+(yFrac_(L)>>3)−1) and            refPicLX as inputs.            -   x_(L) is equal to 0.            -   x_(L) is equal to sbWidth+1.            -   y_(L) is equal to 0.            -   y_(L) is equal to sbHeight+1.        -   Otherwise, the prediction luma sample value            predSamplesLX[xL][yL] is derived by invoking the luma sample            8-tap interpolation filtering process as specified in clause            8.5.6.3.2 with (xIntL−(brdExtSize>0?1:0),            yIntL−(brdExtSize>0?1:0)), (xFracL, yFracL), (xSbInt_(L),            ySbInt_(L),), refPicLX, hpelIfIdx, sbWidth, sbHeight and            (xSb, ySb) as inputs.

    -   Otherwise (cIdx is not equal to 0), the following applies:        -   Let (xIntC, yIntC) be a chroma location given in full-sample            units and (xFracC, yFracC) be an offset given in 1/32 sample            units. These variables are used only in this clause for            specifying general fractional-sample locations inside the            reference sample arrays refPicLX.        -   The top-left coordinate of the bounding block for reference            sample padding (xSbIntC, ySbIntC) is set equal to            ((xSb/SubWidthC)+(mvLX[0]>>5),            (ySb/SubHeightC)+(mvLX[1]>>5)).        -   For each chroma sample location (xC=0 . . . sbWidth−1, yC=0            . . . sbHeight−1) inside the prediction chroma sample arrays            predSamplesLX, the corresponding prediction chroma sample            value predSamplesLX[xC][yC] is derived as follows:            -   Let (refxSbc, refySbc) and (refxc, refyc) be chroma                locations pointed to by a motion vector (mvLX[0],                mvLX[1]) given in 1/32-sample units. The variables                refxSb_(C), refySb_(C), refx_(C) and refy_(C) are                derived as follows:

refxSb_(C)=((

/SubWidthC<<5)+mvLX[0])*hori_scale_fp  (8-763)

refx_(C)=((Sign(refxSb_(C))*((Abs(refxSb_(C))+256)>>9)+xC*((hori_scale_fp+8)>>4))

+16)>>5  (8-764)

refySb_(C)=((

/SubHeightC<<5)+mvLX[1])*vert_scale_fp  (8-765)

refy_(C)=((Sign(refySbc)*((Abs(refySbc)+256)>>9)+yC*((vert_scale_fp+8)>>4))

+16)>>5  (8-766)

-   -   -   -   The variables xInt_(C), yInt_(C), xFrac_(C) and                yFrac_(C) are derived as follows:

xInt_(C)=refx_(C)>>5  (8-767)

yInt_(C)=refy_(C)>>5  (8-768)

xFrac_(C)=refy_(C)&31  (8-769)

yFrac_(C)=refy_(C)&31  (8-770)

5.5. Embodiment 1 of Reference Sample Position Clipping

8.5.6.3.1 General

Inputs to this process are:

-   -   a luma location (xSb, ySb) specifying the top-left sample of the        current coding subblock relative to the top-left luma sample of        the current picture,    -   a variable sbWidth specifying the width of the current coding        subblock,    -   a variable sbHeight specifying the height of the current coding        subblock,    -   a motion vector offset mvOffset,    -   a refined motion vector refMvLX,    -   the selected reference picture sample array refPicLX,    -   the half sample interpolation filter index hpelIfIdx,    -   the bi-directional optical flow flag bdofFlag,    -   a variable cIdx specifying the colour component index of the        current block.        Outputs of this process are:    -   an (sbWidth+brdExtSize)×(sbHeight+brdExtSize) array        predSamplesLX of prediction sample values.        The prediction block border extension size brdExtSize is derived        as follows:

brdExtSize=(bdofFlag∥(inter_affine_flag[xSb][ySb]&&sps_affine_prof_enabled_flag))?2:0  (8-752)

The variable fRefWidth is set equal to the PicOutputWidthL of thereference picture in luma samples.The variable fRefHeight is set equal to PicOutputHeightL of thereference picture in luma samples.The motion vector mvLX is set equal to (refMvLX−mvOffset).

-   -   If cIdx is equal to 0, the following applies:        -   The scaling factors and their fixed-point representations            are defined as

hori_scale_fp=((fRefWidth<<14)+(PicOutputWidthL>>1))/PicOutputWidthL  (8-753)

vert_scale_fp=((fRefHeight<<14)+(PicOutputHeightL>>1))/PicOutputHeightL  (8-754)

-   -   -   Let (xIntL, yIntL) be a luma location given in full-sample            units and (xFracL, yFracL) be an offset given in 1/16-sample            units. These variables are used only in this clause for            specifying fractional-sample locations inside the reference            sample arrays refPicLX.        -   The top-left coordinate of the bounding block for reference            sample padding (xSbInt_(L), ySbInt_(L)) is set equal to            (xSb+(mvLX[0]>>4), ySb+(mvLX[1]>>4)).        -   For each luma sample location (x_(L)=0 . . .            sbWidth−1+brdExtSize, y_(L)=0 . . . sbHeight−1+brdExtSize)            inside the prediction luma sample array predSamplesLX, the            corresponding prediction luma sample value            predSamplesLX[x_(L)][y_(L)] is derived as follows:            -   Let (refxSb_(L), refySb_(L)) and (refx_(L), refy_(L)) be                luma locations pointed to by a motion vector                (refMvLX[0], refMvLX[1]) given in 1/16-sample units. The                variables refxSb_(L), refx_(L), refySb_(L), and refy_(L)                are derived as follows:

refxSb_(L)=((xSb<<4)+refMvLX[0])*hori_scale_fp  (8-755)

refx_(L)=((Sign(refxSb)*((Abs(refxSb)+128)>>8)+x_(L)*((hori_scale_fp+8)>>4))+32)>>6  (8-756)

refySb_(L)=((ySb<<4)+refMvLX[1])*vert_scale_fp  (8-757)

refy_(L)=((Sign(refySb)*((Abs(refySb)+128)>>8)+y_(L)*((vert_scale_fp+8)>>4))+32)>>6  (8-758)

-   -   -   -   The variables xInt_(L), yInt_(L), xFrac_(L) and                yFrac_(L) are derived as follows:

xInt_(L)=

  (8-759)

yInt_(L)=

  (8-760)

xFrac_(L)=refx_(L)&15  (8-761)

yFrac_(L)=refy_(L)&15  (8-762)

-   -   -   If bdofFlag is equal to TRUE or            (sps_affine_prof_enabled_flag is equal to TRUE and            inter_affine_flag[xSb][ySb] is equal to TRUE), and one or            more of the following conditions are true, the prediction            luma sample value predSamplesLX[x_(L)][y_(L)] is derived by            invoking the luma integer sample fetching process as            specified in clause 8.5.6.3.3 with            (xInt_(L)+(xFrac_(L)>>3)−1), yInt_(L)+(yFrac_(L)>>3)−1) and            refPicLX as inputs.            -   x_(L) is equal to 0.            -   x_(L) is equal to sbWidth+1.            -   y_(L) is equal to 0.            -   y_(L) is equal to sbHeight+1.        -   Otherwise, the prediction luma sample value            predSamplesLX[xL][yL] is derived by invoking the luma sample            8-tap interpolation filtering process as specified in clause            8.5.6.3.2 with (xIntL−(brdExtSize>0?1:0),            yIntL−(brdExtSize>0?1:0)), (xFracL, yFracL), (xSbInt_(L),            ySbInt_(L)), refPicLX, hpelIfIdx, sbWidth, sbHeight and            (xSb, ySb) as inputs.

    -   Otherwise (cIdx is not equal to 0), the following applies:        -   Let (xIntC, yIntC) be a chroma location given in full-sample            units and (xFracC, yFracC) be an offset given in 1/32 sample            units. These variables are used only in this clause for            specifying general fractional-sample locations inside the            reference sample arrays refPicLX.        -   The top-left coordinate of the bounding block for reference            sample padding (xSbInt_(C), ySbInt_(C)) is set equal to            ((xSb/SubWidthC)+(mvLX[0]>>5),            (ySb/SubHeightC)+(mvLX[1]>>5)).        -   For each chroma sample location (xC=0 . . . sbWidth−1, yC=0            . . . sbHeight−1) inside the prediction chroma sample arrays            predSamplesLX, the corresponding prediction chroma sample            value predSamplesLX[xC][yC] is derived as follows:            -   Let (refxSb_(C), refySb_(C)) and (refx_(C), refy_(C)) be                chroma locations pointed to by a motion vector (mvLX[0],                mvLX[1]) given in 1/32-sample units. The variables                refxSb_(C), refySb_(C), refx_(C) and refy_(C) are                derived as follows:

refxSb_(C)=((xSb/SubWidthC<<5)+mvLX[0])*hori_scale_fp  (8-763)

refx_(C)=((Sign(refxSb_(C))*((Abs(refxSb_(C))+256)>>9)+xC*((hori_scale_fp+8)>>4))+16)>>5  (8-764)

refySb_(C)=((ySb/SubHeightC<<5)+mvLX[1])*vert_scale_fp  (8-765)

refy_(C)=((Sign(refySb_(C))*((Abs(refySb_(C))+256)>>9)+yC*((vert_scale_fp+8)>>4))+16)>>5  (8-766)

The variables xInt_(C), yInt_(C), xFrac_(C) and yFrac_(C) are derived asfollows:

xInt_(C)=

  (8-767)

yInt_(C)=

  (8-768)

xFrac_(C)=refy_(C)&31  (8-769)

yFrac_(C)=refy_(C)&31  (8-770)

-   -   -   The prediction sample value predSamplesLX[xC][yC] is derived            by invoking the process specified in clause 8.5.6.3.4 with            (xIntC, yIntC), (xFracC, yFracC), (xSbIntC, ySbIntC),            sbWidth, sbHeight and refPicLX as inputs.

5.6. Embodiment 2 of Reference Sample Position Clipping

8.5.6.3.1 General

Inputs to this process are:

-   -   a luma location (xSb, ySb) specifying the top-left sample of the        current coding subblock relative to the top-left luma sample of        the current picture,    -   a variable sbWidth specifying the width of the current coding        subblock,    -   a variable sbHeight specifying the height of the current coding        subblock,    -   a motion vector offset mvOffset,    -   a refined motion vector refMvLX,    -   the selected reference picture sample array refPicLX,    -   the half sample interpolation filter index hpelIfIdx,    -   the bi-directional optical flow flag bdofFlag,    -   a variable cIdx specifying the colour component index of the        current block.        Outputs of this process are:    -   an (sbWidth+brdExtSize)×(sbHeight+brdExtSize) array        predSamplesLX of prediction sample values.        The prediction block border extension size brdExtSize is derived        as follows:

brdExtSize=(bdofFlag∥(inter_affine_flag[xSb][ySb]&&sps_affine_prof_enabled_flag))?2:0  (8-752)

The variable fRefWidth is set equal to the PicOutputWidthL of thereference picture in luma samples.The variable fRefHeight is set equal to PicOutputHeightL of thereference picture in luma samples.

The motion vector mvLX is set equal to (refMvLX−mvOffset).

-   -   If cIdx is equal to 0, the following applies:        -   The scaling factors and their fixed-point representations            are defined as

hori_scale_fp=((fRefWidth<<14)+(PicOutputWidthL>>1))/PicOutputWidthL  (8-753)

vert_scale_fp=((fRefHeight<<14)+(PicOutputHeightL>>1))/PicOutputHeightL  (8-754)

-   -   -   Let (xIntL, yIntL) be a luma location given in full-sample            units and (xFracL, yFracL) be an offset given in 1/16-sample            units. These variables are used only in this clause for            specifying fractional-sample locations inside the reference            sample arrays refPicLX.        -   The top-left coordinate of the bounding block for reference            sample padding (xSbInt_(L), ySbInt_(L)) is set equal to            (xSb+(mvLX[0]>>4), ySb+(mvLX[1]>>4)).        -   For each luma sample location (x_(L)=0 . . .            sbWidth−1+brdExtSize, y_(L)=0 . . . sbHeight−1+brdExtSize)            inside the prediction luma sample array predSamplesLX, the            corresponding prediction luma sample value            predSamplesLX[x_(L)][y_(L)] is derived as follows:            -   Let (refxSb_(L), refySb_(L)) and (refx_(L), refy_(L)) be                luma locations pointed to by a motion vector                (refMvLX[0], refMvLX[1]) given in 1/16-sample units. The                variables refxSb_(L), refx_(L), refySb_(L), and refy_(L)                are derived as follows:

refxSb_(L)=((xSb<<4)+refMvLX[0])*hori_scale_fp  (8-755)

refx_(L)=((Sign(refxSb)*((Abs(refxSb)+128)>>8)+x_(L)*((hori_scale_fp+8)>>4))+32)>>6  (8-756)

refySb_(L)=((ySb<<4)+refMvLX[1])*vert_scale_fp  (8-757)

refyL=((Sign(refySb)*((Abs(refySb)+128)>>8)+yL*((vert_scale_fp+8)>>4))+32)>>6  (8-758)

-   -   -   -   The variables xInt_(L), yInt_(L), xFrac_(L) and                yFrac_(L) are derived as follows:

xInt_(L)=

  (8-759)

yInt_(L)=

  (8-760)

xFrac_(L)=refx_(L)&15  (8-761)

yFrac_(L)=refy_(L)& 15  (8-762)

-   -   -   If bdofFlag is equal to TRUE or            (sps_affine_prof_enabled_flag is equal to TRUE and            inter_affine_flag[xSb][ySb] is equal to TRUE), and one or            more of the following conditions are true, the prediction            luma sample value predSamplesLX[x_(L)][y_(L)] is derived by            invoking the luma integer sample fetching process as            specified in clause 8.5.6.3.3 with            (xInt_(L)+(xFrac_(L)>>3)−1), yInt_(L)+(yFrac_(L)>>3)−1) and            refPicLX as inputs.            -   x_(L) is equal to 0.            -   x_(L) is equal to sbWidth+1.            -   y_(L) is equal to 0.            -   y_(L) is equal to sbHeight+1.        -   Otherwise, the prediction luma sample value            predSamplesLX[xL][yL] is derived by invoking the luma sample            8-tap interpolation filtering process as specified in clause            8.5.6.3.2 with (xInt_(L)−(brdExtSize>0?1:0),            yInt_(L)−(brdExtSize>0?1:0)), (xSbInt_(L), ySbInt_(L)),            refPicLX, hpelIfIdx, sbWidth, sbHeight and (xSb, ySb) as            inputs.

    -   Otherwise (cIdx is not equal to 0), the following applies:        -   Let (xIntC, yIntC) be a chroma location given in full-sample            units and (xFracC, yFracC) be an offset given in 1/32 sample            units. These variables are used only in this clause for            specifying general fractional-sample locations inside the            reference sample arrays refPicLX.        -   The top-left coordinate of the bounding block for reference            sample padding (xSbIntC, ySbIntC) is set equal to            ((xSb/SubWidthC)+(mvLX[0]>>5),            (ySb/SubHeightC)+(mvLX[1]>>5)).        -   For each chroma sample location (xC=0 . . . sbWidth−1, yC=0            . . . sbHeight−1) inside the prediction chroma sample arrays            predSamplesLX, the corresponding prediction chroma sample            value predSamplesLX[xC][yC] is derived as follows:            -   Let (refxSb_(C), refySb_(C)) and (refx_(C), refy_(C)) be                chroma locations pointed to by a motion vector (mvLX[0],                mvLX[1]) given in 1/32-sample units. The variables                refxSb_(C), refySb_(C), refx_(C) and refy_(C) are                derived as follows:

refxSb_(C)=((xSb/SubWidthC<<5)+mvLX[0])*hori_scale_fp  (8-763)

refx_(C)=((Sign(refxSb_(C))*((Abs(refxSb_(C))+256)>>9)+xC*((hori_scale_fp+8)>>4))+16)>>5  (8-764)

refySb_(C)=((ySb/SubHeightC<<5)+mvLX[1])*vert_scale_fp  (8-765)

refy_(C)=((Sign(refySb_(C))*((Abs(refySb_(C))+256)>>9)+yC*((vert_scale_fp+8)>>4))+16)>>5  (8-766)

-   -   -   -   The variables xInt_(C), yInt_(C), xFrac_(C) and                yFrac_(C) are derived as follows:

xInt_(C)=

   (8-767)

yIntc=Clip3(fRefTopOff/SubHeightC,(fRefHeight+fRefTopOff)/SubHeightC−1,refyC>>5)  (8-768)

xFrac_(C)=refy_(C)&31  (8-769)

yFrac_(C)=refy_(C)&31  (8-770)

-   -   -   The prediction sample value predSamplesLX[xC][yC] is derived            by invoking the process specified in clause 8.5.6.3.4 with            (xIntC, yIntC), (xFracC, yFracC), (xSbIntC, ySbIntC),            sbWidth, sbHeight and refPicLX as inputs.

5.7. Embodiment of Usage of Coding Tools

5.7.1 BDOF on/Off Control

-   -   The variable currPic specifies the current picture and the        variable bdofFlag is derived as follows:        -   If all of the following conditions are true, bdofFlag is set            equal to TRUE.            -   sps_bdof_enabled_flag is equal to 1 and                slice_disable_bdof_dmvr_flag is equal to 0.

            -   predFlagL0[xSbIdx][ySbIdx] and                predFlagL1[xSbIdx][ySbIdx] are both equal to 1.

            -   DiffPicOrderCnt(currPic, RefPicList[0][refIdxL0]) is                equal to DiffPicOrderCnt(RefPicList[1][refIdxL1],                currPic).

            -   RefPicList[0][refIdxL0] is a short-term reference                picture and RefPicList[1][refIdxL1] is a short-term                reference picture.

            -   MotionModeIIdc[xCb][yCb] is equal to 0.

            -   merge_subblock_flag[xCb][yCb] is equal to 0.

            -   sym_mvd_flag[xCb][yCb] is equal to 0.

            -   ciip_flag[xCb][yCb] is equal to 0.

            -   BcwIdx[xCb][yCb] is equal to 0.

            -   luma_weight_l0_flag[refIdxL0] and                luma_weight_l1_flag[refIdxL1] are both equal to 0.

            -   cbWidth is greater than or equal to 8.

            -   cbHeight is greater than or equal to 8.

            -   cbHeight*cbWidth is greater than or equal to 128.

            -   

            -   cIdx is equal to 0.        -   Otherwise, bdofFlag is set equal to FALSE.

5.7.2 DMVR on/Off Control

-   -   When all of the following conditions are true, dmvrFlag is set        equal to 1:        -   sps_dmvr_enabled_flag is equal to 1 and            slice_disable_bdof_dmvr_flag is equal to 0

        -   general_merge_flag[xCb][yCb] is equal to 1

        -   both predFlagL0 [0][0] and predFlagL1 [0][0] are equal to 1

        -   mmvd_merge_flag[xCb][yCb] is equal to 0

        -   ciip_flag[xCb][yCb] is equal to 0

        -   DiffPicOrderCnt(currPic, RefPicList[0][refIdxL0]) is equal            to DiffPicOrderCnt(RefPicList[1][refIdxL1], currPic)

        -   RefPicList[0][refIdxL0] is a short-term reference picture            and RefPicList[1][refIdxL1] is a short-term reference            picture.

        -   BcwIdx[xCb][yCb] is equal to 0

        -   Both luma_weight_l0_flag[refIdxL0] and            luma_weight_l1_flag[refIdxL1] are equal to 0

        -   cbWidth is greater than or equal to 8

        -   cbHeight is greater than or equal to 8

        -   cbHeight*cbWidth is greater than or equal to 128

        -   

5.7.3 PROF on/Off Control for a Reference Picture List X

The variable cbProfFlagLX is derived as follows:

-   -   If one or more of the following conditions are true,        cbProfFlagLX is set equal to FALSE.        -   sps_affine_prof_enabled_flag is equal to 0.

        -   fallbackModeTriggered is equal to 1.

        -   numCpMv is equal to 2 and cpMvLX[1][0] is equal to            cpMvLX[0][0] and cpMvLX[1][1] is equal to cpMvLX[0][1].

        -   numCpMv is equal to 3 and cpMvLX[1][0] is equal to            cpMvLX[0][0] and cpMvLX[1][1] is equal to cpMvLX[0][1] and            cpMvLX[2][0] is equal to cpMvLX[0][0] and cpMvLX[2][1] is            equal to cpMvLX[0][1].

        -   

        -   [[The pic_width_in_luma_samples of the reference picture            refPicLX associated with the refIdxLX is not equal to the            pic_width_in_luma_samples of the current picture,            respectively.

        -   The pic_height_in_luma_samples of the reference picture            refPicLX associated with the refIdxLX is not equal to the            pic_height_in_luma_samples of the current picture,            respectively.]]    -   Otherwise, cbProfFlagLX set equal to TRUE.

5.7.4 PROF on/Off Control for a Reference Picture List X (a SecondEmbodiment)

The variable cbProfFlagLX is derived as follows:

-   -   If one or more of the following conditions are true,        cbProfFlagLX is set equal to FALSE.        -   sps_affine_prof_enabled_flag is equal to 0.

        -   fallbackModeTriggered is equal to 1.

        -   numCpMv is equal to 2 and cpMvLX[1][0] is equal to            cpMvLX[0][0] and cpMvLX[1][1] is equal to cpMvLX[0][1].

        -   numCpMv is equal to 3 and cpMvLX[1][0] is equal to            cpMvLX[0][0] and cpMvLX[1][1] is equal to cpMvLX[0][1] and            cpMvLX[2][0] is equal to cpMvLX[0][0] and cpMvLX[2][1] is            equal to cpMvLX[0][1].

        -   

        -   [[The pic_width_in_luma_samples of the reference picture            refPicLX associated with the refIdxLX is not equal to the            pic_width_in_luma_samples of the current picture,            respectively.

        -   The pic_height_in_luma_samples of the reference picture            refPicLX associated with the refIdxLX is not equal to the            pic_height_in_luma_samples of the current picture,            respectively.]]

        -   Otherwise, cbProfFlagLX set equal to TRUE.

6. Example Implementations of the Disclosed Technology

FIG. 5 is a block diagram of a video processing apparatus 500. Theapparatus 500 may be used to implement one or more of the methodsdescribed herein. The apparatus 500 may be embodied in a smartphone,tablet, computer, Internet of Things (IoT) receiver, and so on. Theapparatus 500 may include one or more processors 502, one or morememories 504 and video processing hardware 506. The processor(s) 502 maybe configured to implement one or more methods described in the presentdocument. The memory (memories) 504 may be used for storing data andcode used for implementing the methods and techniques described herein.The video processing hardware 506 may be used to implement, in hardwarecircuitry, some techniques described in the present document, and may bepartly or completely be a part of the processors 502 (e.g., graphicsprocessor core GPU or other signal processing circuitry).

In the present document, the term “video processing” or coding may referto video encoding, video decoding, video compression or videodecompression. For example, video compression algorithms may be appliedduring conversion from pixel representation of a video to acorresponding bitstream representation or vice versa. The bitstreamrepresentation of a current video block may, for example, correspond tobits that are either co-located or spread in different places within thebitstream, as is defined by the syntax. For example, a macroblock may beencoded in terms of transformed and coded error residual values and alsousing bits in headers and other fields in the bitstream.

It will be appreciated that the disclosed methods and techniques willbenefit video encoder and/or decoder embodiments incorporated withinvideo processing devices such as smartphones, laptops, desktops, andsimilar devices by allowing the use of the techniques disclosed in thepresent document.

FIG. 6 is a flowchart for an example method 600 of video processing. Themethod 600 includes, at 610, performing a conversion between a currentvideo block and a coded representation of the current video block,wherein, during the conversion, if a resolution and/or a size of areference picture is different from a resolution and/or a size of thecurrent video block, a same interpolation filter is applied to a groupof adjacent or non-adjacent samples predicted using the current videoblock.

Some embodiments may be described using the following clause-basedformat.

-   -   1. A method of video processing, comprising:        -   performing a conversion between a current video block and a            coded representation of the current video block, wherein,            during the conversion, if a resolution and/or a size of a            reference picture is different from a resolution and/or a            size of the current video block, a same interpolation filter            is applied to a group of adjacent or non-adjacent samples            predicted using the current video block.    -   2. The method of clause 1, wherein the same interpolation filter        is a vertical interpolation filter.    -   3. The method of clause 1, wherein the same interpolation filter        is a horizontal interpolation filter.    -   4. The method of clause 1, wherein the group of adjacent or        non-adjacent samples include all samples located in a region of        the current video block.    -   5. The method of clause 4, wherein the current video blocks is        divided into multiple rectangles each of size M×N.    -   6. The method of clause 5, wherein M and/or N are        pre-determined.    -   7. The method of clause 5, wherein M and/or N are derived from        dimensions of the current video block.    -   8. The method of clause 5, wherein M and/or N are signaled in        the coded representation of the current video block.    -   9. The method of clause 1, wherein the group of samples share a        same motion vector.    -   10. The method of clause 9, wherein the group of samples share a        same horizontal component and/or a same fractional part of a        horizontal component.    -   11. The method of clause 9, wherein the group of samples share a        same vertical component and/or a same fractional part of a        vertical component.    -   12. The method of one or more of clauses 9-11, wherein the same        motion vector or components thereof satisfy one or more rules        based at least on one of: the resolution of the reference        picture, the size of the reference picture, the resolution of        the current video block, the size of the current video block, or        a precision value.    -   13. The method of one or more of clauses 9-11, wherein the same        motion vector or components thereof corresponds to a motion        information of a sample located in the current video block.    -   14. The method of one or more of clauses 9-11, wherein the same        motion vector or components thereof are set to a motion        information of a virtual sample located inside or outside the        group.    -   15. A method of video processing, comprising:        -   performing a conversion between a current video block and a            coded representation of the current video block, wherein,            during the conversion, if a resolution and/or a size of a            reference picture is different from a resolution and/or a            size of the current video block, wherein blocks predicted            using the current video block are only allowed to use            integer-valued motion information related to the current            block.    -   16. The method of clause 15, wherein the integer-valued motion        information is derived by rounding an original motion        information of the current video block.    -   17. The method of clause 15, wherein the original motion        information of the current video block is in a horizontal        direction and/or a vertical direction.    -   18. A method of video processing, comprising:        -   performing a conversion between a current video block and a            coded representation of the current video block, wherein,            during the conversion, if a resolution and/or a size of a            reference picture is different from a resolution and/or a            size of the current video block, an interpolation filter is            applied to derive blocks predicted using the current video            block, and wherein the interpolation filter is selected            based on a rule.    -   19. The method of clause 18, whether the rule is related to the        resolution and/or the size of the reference picture relative to        the resolution and/or the size of the current video block.    -   20. The method of clause 18, wherein the interpolation filter is        a vertical interpolation filter.    -   21. The method of clause 18, wherein the interpolation filter is        a horizontal interpolation filter.    -   22. The method of clause 18, wherein the interpolation filter is        one of: a 1-tap filter, a bilinear filter, a 4-tap filter, or a        6-tap filter.    -   23. The method of clause 22, wherein the interpolation filter is        used as part of other steps of the conversion.    -   24. The method of clause 18, wherein the interpolation filter        includes a use of padding samples.    -   25. The method of clause 18, wherein a use of the interpolation        filter depends on a color component of a sample of the current        video block.    -   26. A method of video processing, comprising:        -   performing a conversion between a current video block and a            coded representation of the current video block, wherein,            during the conversion, if a resolution and/or a size of a            reference picture is different from a resolution and/or a            size of the current video block, selectively applying a            deblocking filter, wherein a strength of the deblocking            filter set in accordance with a rule related to the            resolution and/or the size of the reference picture relative            to the resolution and/or the size of the current video            block.    -   27. The method of clause 27, wherein the strength of the        deblocking filter varies from one video block to another.    -   28. A method of video processing, comprising:        -   performing a conversion between a current video block and a            coded representation of the current video block, wherein,            during the conversion, if a sub-picture of the current video            block exists, a conformance bitstream satisfies a rule            related to the resolution and/or the size of the reference            picture relative to the resolution and/or the size of the            current video block.    -   29. The method of clause 28, further comprising:        -   splitting the current video block into one or more            sub-pictures, wherein the splitting depends at least on the            resolution of the current video block.    -   30. A method of video processing, comprising:        -   performing a conversion between a current video block and a            coded representation of the current video block, wherein,            during the conversion, a reference picture of the current            video block is resampled in accordance with a rule based on            dimensions of the current video block.    -   31. A method of video processing, comprising:        -   performing a conversion between a current video block and a            coded representation of the current video block, wherein,            during the conversion, a use of a coding tool on the current            video block is selectively enabled or disabled depending on            a resolution/size of a reference picture of the current            video block relative to a resolution/size of the current            video block.    -   32. The method of one or more of the aforementioned clauses,        wherein the group of samples are located in a conformance        window.    -   33. The method of clause 32, wherein the conformance window is        rectangular in shape.    -   34. The method of any one or more of the aforementioned clauses,        wherein the resolution pertains to a resolution of the        coded/decoded video block or a resolution of the conformance        window in the coded/decoded video block.    -   35. The method of any one or more of the aforementioned clauses,        wherein the size pertains to a size of the coded/decoded video        block or a size of the conformance window in the coded/decoded        video block.    -   36. The method of any one or more of the aforementioned clauses,        wherein the dimensions pertain to dimensions of the        coded/decoded video block or dimensions of the conformance        window in the coded/decoded video block.    -   37. The method of clause 32, wherein the conformance window is        defined by a set of conformance cropping window parameters.    -   38. The method of clause 37, wherein at least a portion of set        of conformance cropping window parameters are implicitly or        explicitly signaled in the coded representation.    -   39. The method of any one or more of the aforementioned clauses,        wherein the set of conformance cropping window parameters is        disallowed to be signaled in the coded representation.    -   40. The method of any one or more of the aforementioned clauses,        wherein a position of the reference sample is derived with        respect to a top-left sample of the current video block in the        conformance window.    -   41. A method of video processing, comprising:        -   performing a conversion between multiple video blocks and            coded representations of the multiple video blocks, wherein,            during the conversion, a first conformance window is defined            for a first video block and a second conformance window for            a second video block, and wherein a ratio of a width and/or            a height of the first conformance window to the second            conformance window is in accordance with a rule based at            least on a conformance bitstream.    -   42. A video decoding apparatus comprising a processor configured        to implement a method recited in one or more of clauses 1 to 41.    -   43. A video encoding apparatus comprising a processor configured        to implement a method recited in one or more of clauses 1 to 41.    -   44. A computer program product having computer code stored        thereon, the code, when executed by a processor, causes the        processor to implement a method recited in any of clauses 1 to        41.    -   45. A method, apparatus or system described in the present        document.

FIG. 9 is a block diagram showing an example video processing system 900in which various techniques disclosed herein may be implemented. Variousimplementations may include some or all of the components of the system900. The system 900 may include input 902 for receiving video content.The video content may be received in a raw or uncompressed format, e.g.,8 or 10 bit multi-component pixel values, or may be in a compressed orencoded format. The input 902 may represent a network interface, aperipheral bus interface, or a storage interface. Examples of networkinterface include wired interfaces such as Ethernet, passive opticalnetwork (PON), etc. and wireless interfaces such as Wi-Fi or cellularinterfaces.

The system 900 may include a coding component 904 that may implement thevarious coding or encoding methods described in the present document.The coding component 904 may reduce the average bitrate of video fromthe input 902 to the output of the coding component 904 to produce acoded representation of the video. The coding techniques are thereforesometimes called video compression or video transcoding techniques. Theoutput of the coding component 904 may be either stored, or transmittedvia a communication connected, as represented by the component 906. Thestored or communicated bitstream (or coded) representation of the videoreceived at the input 902 may be used by the component 908 forgenerating pixel values or displayable video that is sent to a displayinterface 910. The process of generating user-viewable video from thebitstream representation is sometimes called video decompression.Furthermore, while certain video processing operations are referred toas “coding” operations or tools, it will be appreciated that the codingtools or operations are used at an encoder and corresponding decodingtools or operations that reverse the results of the coding will beperformed by a decoder.

Examples of a peripheral bus interface or a display interface mayinclude universal serial bus (USB) or high definition multimediainterface (HDMI) or Displayport, and so on. Examples of storageinterfaces include SATA (serial advanced technology attachment), PCI,IDE interface, and the like. The techniques described in the presentdocument may be embodied in various electronic devices such as mobilephones, laptops, smartphones or other devices that are capable ofperforming digital data processing and/or video display.

FIG. 10 is a block diagram that illustrates an example video codingsystem 100 that may utilize the techniques of this disclosure.

As shown in FIG. 10 , video coding system 100 may include a sourcedevice 110 and a destination device 120. Source device 110 generatesencoded video data which may be referred to as a video encoding device.Destination device 120 may decode the encoded video data generated bysource device 110 which may be referred to as a video decoding device.

Source device 110 may include a video source 112, a video encoder 114,and an input/output (I/O) interface 116.

Video source 112 may include a source such as a video capture device, aninterface to receive video data from a video content provider, and/or acomputer graphics system for generating video data, or a combination ofsuch sources. The video data may comprise one or more pictures. Videoencoder 114 encodes the video data from video source 112 to generate abitstream. The bitstream may include a sequence of bits that form acoded representation of the video data. The bitstream may include codedpictures and associated data. The coded picture is a codedrepresentation of a picture. The associated data may include sequenceparameter sets, picture parameter sets, and other syntax structures. I/Ointerface 116 may include a modulator/demodulator (modem) and/or atransmitter. The encoded video data may be transmitted directly todestination device 120 via I/O interface 116 through network 130 a. Theencoded video data may also be stored onto a storage medium/server 130 bfor access by destination device 120.

Destination device 120 may include an I/O interface 126, a video decoder124, and a display device 122.

I/O interface 126 may include a receiver and/or a modem. I/O interface126 may acquire encoded video data from the source device 110 or thestorage medium/server 130 b. Video decoder 124 may decode the encodedvideo data. Display device 122 may display the decoded video data to auser. Display device 122 may be integrated with the destination device120, or may be external to destination device 120 which be configured tointerface with an external display device.

Video encoder 114 and video decoder 124 may operate according to a videocompression standard, such as the High Efficiency Video Coding (HEVC)standard, Versatile Video Coding (VVC) standard and other current and/orfurther standards.

FIG. 11 is a block diagram illustrating an example of video encoder 200,which may be video encoder 114 in the system 100 illustrated in FIG. 10.

Video encoder 200 may be configured to perform any or all of thetechniques of this disclosure. In the example of FIG. 9 , video encoder200 includes a plurality of functional components. The techniquesdescribed in this disclosure may be shared among the various componentsof video encoder 200. In some examples, a processor may be configured toperform any or all of the techniques described in this disclosure.

The functional components of video encoder 200 may include a partitionunit 201, a predication unit 202 which may include a mode select unit203, a motion estimation unit 204, a motion compensation unit 205 and anintra prediction unit 206, a residual generation unit 207, a transformunit 208, a quantization unit 209, an inverse quantization unit 210, aninverse transform unit 211, a reconstruction unit 212, a buffer 213, andan entropy encoding unit 214.

In other examples, video encoder 200 may include more, fewer, ordifferent functional components. In an example, predication unit 202 mayinclude an intra block copy (IBC) unit. The IBC unit may performpredication in an IBC mode in which at least one reference picture is apicture where the current video block is located.

Furthermore, some components, such as motion estimation unit 204 andmotion compensation unit 205 may be highly integrated, but arerepresented in the example of FIG. 5 separately for purposes ofexplanation.

Partition unit 201 may partition a picture into one or more videoblocks. Video encoder 200 and video decoder 300 may support variousvideo block sizes.

Mode select unit 203 may select one of the coding modes, intra or inter,e.g., based on error results, and provide the resulting intra- orinter-coded block to a residual generation unit 207 to generate residualblock data and to a reconstruction unit 212 to reconstruct the encodedblock for use as a reference picture. In some example, Mode select unit203 may select a combination of intra and inter predication (CIIP) modein which the predication is based on an inter predication signal and anintra predication signal. Mode select unit 203 may also select aresolution for a motion vector (e.g., a sub-pixel or integer pixelprecision) for the block in the case of inter-predication.

To perform inter prediction on a current video block, motion estimationunit 204 may generate motion information for the current video block bycomparing one or more reference frames from buffer 213 to the currentvideo block. Motion compensation unit 205 may determine a predictedvideo block for the current video block based on the motion informationand decoded samples of pictures from buffer 213 other than the pictureassociated with the current video block.

Motion estimation unit 204 and motion compensation unit 205 may performdifferent operations for a current video block, for example, dependingon whether the current video block is in an I slice, a P slice, or a Bslice.

In some examples, motion estimation unit 204 may perform uni-directionalprediction for the current video block, and motion estimation unit 204may search reference pictures of list 0 or list 1 for a reference videoblock for the current video block. Motion estimation unit 204 may thengenerate a reference index that indicates the reference picture in list0 or list 1 that contains the reference video block and a motion vectorthat indicates a spatial displacement between the current video blockand the reference video block. Motion estimation unit 204 may output thereference index, a prediction direction indicator, and the motion vectoras the motion information of the current video block. Motioncompensation unit 205 may generate the predicted video block of thecurrent block based on the reference video block indicated by the motioninformation of the current video block.

In other examples, motion estimation unit 204 may perform bi-directionalprediction for the current video block, motion estimation unit 204 maysearch the reference pictures in list 0 for a reference video block forthe current video block and may also search the reference pictures inlist 1 for another reference video block for the current video block.Motion estimation unit 204 may then generate reference indexes thatindicate the reference pictures in list 0 and list 1 containing thereference video blocks and motion vectors that indicate spatialdisplacements between the reference video blocks and the current videoblock. Motion estimation unit 204 may output the reference indexes andthe motion vectors of the current video block as the motion informationof the current video block. Motion compensation unit 205 may generatethe predicted video block of the current video block based on thereference video blocks indicated by the motion information of thecurrent video block.

In some examples, motion estimation unit 204 may output a full set ofmotion information for decoding processing of a decoder.

In some examples, motion estimation unit 204 may do not output a fullset of motion information for the current video. Rather, motionestimation unit 204 may signal the motion information of the currentvideo block with reference to the motion information of another videoblock. For example, motion estimation unit 204 may determine that themotion information of the current video block is sufficiently similar tothe motion information of a neighboring video block.

In one example, motion estimation unit 204 may indicate, in a syntaxstructure associated with the current video block, a value thatindicates to the video decoder 300 that the current video block has thesame motion information as the another video block.

In another example, motion estimation unit 204 may identify, in a syntaxstructure associated with the current video block, another video blockand a motion vector difference (MVD). The motion vector differenceindicates a difference between the motion vector of the current videoblock and the motion vector of the indicated video block. The videodecoder 300 may use the motion vector of the indicated video block andthe motion vector difference to determine the motion vector of thecurrent video block.

As discussed above, video encoder 200 may predictively signal the motionvector. Two examples of predictive signaling techniques that may beimplemented by video encoder 200 include advanced motion vectorpredication (AMVP) and merge mode signaling.

Intra prediction unit 206 may perform intra prediction on the currentvideo block. When intra prediction unit 206 performs intra prediction onthe current video block, intra prediction unit 206 may generateprediction data for the current video block based on decoded samples ofother video blocks in the same picture. The prediction data for thecurrent video block may include a predicted video block and varioussyntax elements.

Residual generation unit 207 may generate residual data for the currentvideo block by subtracting (e.g., indicated by the minus sign) thepredicted video block(s) of the current video block from the currentvideo block. The residual data of the current video block may includeresidual video blocks that correspond to different sample components ofthe samples in the current video block.

In other examples, there may be no residual data for the current videoblock for the current video block, for example in a skip mode, andresidual generation unit 207 may not perform the subtracting operation.

Transform processing unit 208 may generate one or more transformcoefficient video blocks for the current video block by applying one ormore transforms to a residual video block associated with the currentvideo block.

After transform processing unit 208 generates a transform coefficientvideo block associated with the current video block, quantization unit209 may quantize the transform coefficient video block associated withthe current video block based on one or more quantization parameter (QP)values associated with the current video block.

Inverse quantization unit 210 and inverse transform unit 211 may applyinverse quantization and inverse transforms to the transform coefficientvideo block, respectively, to reconstruct a residual video block fromthe transform coefficient video block. Reconstruction unit 212 may addthe reconstructed residual video block to corresponding samples from oneor more predicted video blocks generated by the predication unit 202 toproduce a reconstructed video block associated with the current blockfor storage in the buffer 213.

After reconstruction unit 212 reconstructs the video block, loopfiltering operation may be performed reduce video blocking artifacts inthe video block.

Entropy encoding unit 214 may receive data from other functionalcomponents of the video encoder 200. When entropy encoding unit 214receives the data, entropy encoding unit 214 may perform one or moreentropy encoding operations to generate entropy encoded data and outputa bitstream that includes the entropy encoded data.

FIG. 12 is a block diagram illustrating an example of video decoder 300which may be video decoder 114 in the system 100 illustrated in FIG. 10.

The video decoder 300 may be configured to perform any or all of thetechniques of this disclosure. In the example of FIG. 10 , the videodecoder 300 includes a plurality of functional components. Thetechniques described in this disclosure may be shared among the variouscomponents of the video decoder 300. In some examples, a processor maybe configured to perform any or all of the techniques described in thisdisclosure.

In the example of FIG. 10 , video decoder 300 includes an entropydecoding unit 301, a motion compensation unit 302, an intra predictionunit 303, an inverse quantization unit 304, an inverse transformationunit 305, and a reconstruction unit 306 and a buffer 307. Video decoder300 may, in some examples, perform a decoding pass generally reciprocalto the encoding pass described with respect to video encoder 200 (e.g.,FIG. 9 ).

Entropy decoding unit 301 may retrieve an encoded bitstream. The encodedbitstream may include entropy coded video data (e.g., encoded blocks ofvideo data). Entropy decoding unit 301 may decode the entropy codedvideo data, and from the entropy decoded video data, motion compensationunit 302 may determine motion information including motion vectors,motion vector precision, reference picture list indexes, and othermotion information. Motion compensation unit 302 may, for example,determine such information by performing the ΔMVP and merge mode.

Motion compensation unit 302 may produce motion compensated blocks,possibly performing interpolation based on interpolation filters.Identifiers for interpolation filters to be used with sub-pixelprecision may be included in the syntax elements.

Motion compensation unit 302 may use interpolation filters as used byvideo encoder 20 during encoding of the video block to calculateinterpolated values for sub-integer pixels of a reference block. Motioncompensation unit 302 may determine the interpolation filters used byvideo encoder 200 according to received syntax information and use theinterpolation filters to produce predictive blocks.

Motion compensation unit 302 may uses some of the syntax information todetermine sizes of blocks used to encode frame(s) and/or slice(s) of theencoded video sequence, partition information that describes how eachmacroblock of a picture of the encoded video sequence is partitioned,modes indicating how each partition is encoded, one or more referenceframes (and reference frame lists) for each inter-encoded block, andother information to decode the encoded video sequence.

Intra prediction unit 303 may use intra prediction modes for examplereceived in the bitstream to form a prediction block from spatiallyadjacent blocks. Inverse quantization unit 303 inverse quantizes, e.g.,de-quantizes, the quantized video block coefficients provided in thebitstream and decoded by entropy decoding unit 301. Inverse transformunit 303 applies an inverse transform.

Reconstruction unit 306 may sum the residual blocks with thecorresponding prediction blocks generated by motion compensation unit202 or intra-prediction unit 303 to form decoded blocks. If desired, adeblocking filter may also be applied to filter the decoded blocks inorder to remove blockiness artifacts. The decoded video blocks are thenstored in buffer 307, which provides reference blocks for subsequentmotion compensation.

FIG. 11 is a flowchart representation of a method of video processing inaccordance with the present technology. The method 1100 includes, atoperation 1110, performing a conversion between a video and a bitstreamrepresentation of the video. The bitstream representation conforms to aformat rule that specifies that applicability of a Decoder-side MotionVector Refinement coding tool and a Bi-Directional Optical Flow codingtool for the video picture are indicated separately in the bitstreamrepresentation.

FIG. 13 is a flowchart representation of a method 1300 of videoprocessing in accordance with the present technology. The method 1300includes, at operation 1310, determining, for a conversion between acurrent picture of a video and a bitstream representation of the video,usage of a coding tool based on a condition associated with a dimensionof a portion of one of multiple reference pictures or the currentpicture. The method 1300 also includes, at operation 1320, performingthe conversion based on the determining.

In some embodiments, the usage comprises whether the coding tool isenabled for the current picture. In some embodiments, the portion of apicture comprises a conformance window outside of which samples aredisposable when outputting the video, a scaling window in which samplesare subject to a resampling operation, or an entirely of the picture. Insome embodiments, the coding tool comprises a Decoder-side Motion VectorRefinement coding tool, a Bi-Directional Optical Flow coding tool, aprediction refinement with optical flow (PROF) coding tool, or aninterpolation filter with a half-pel precision for motion compensation.In some embodiments, the coding tool further comprises a temporal motionvector prediction coding tool, a multiple transform sets coding tool, across-component adaptive loop filtering coding tool, a geometricpartitioning coding tool, a blending process for a coding tool thatsplits a block into multiple partitions, a coding tool that requiresstored information in a picture different than the current picture, acoding tool that generates a pairwise merge candidate, a bi-predictionwith coding-unit level weights, a weighted prediction coding tool, anaffine prediction coding tool, or an adaptive motion vector resolutioncoding tool.

In some embodiments, the coding tool is disabled in case the conditionspecifying the dimension in the portion of at least one of the multiplereference pictures is different than a dimension of the current pictureis satisfied. In some embodiments, the dimension of the portion ismodified for the determining. In some embodiments, the usage of thecoding tool is based on at least one of (1) a width of the picture minusone or more horizontal offsets, or (2) a height of the picture minus oneor more vertical offsets. In some embodiments, the one or morehorizontal offsets comprise a left offset for a scaling window. In someembodiments, the one or more vertical offsets comprise a top offset fora scaling window. In some embodiments, the one or more horizontaloffsets comprise a right offset and a left offset for a scaling window.In some embodiments, the one or more vertical offsets comprise a bottomoffset and top offset for a scaling window. In some embodiments, the oneor more horizontal offsets comprise a value based on scaling a sum of aright offset and a left offset for a scaling window. In someembodiments, the one or more vertical offsets comprise a value based onscaling a sum of a bottom offset and top offset for a scaling window.

In some embodiments, the coding tool is disabled in case the conditionspecifying dimensions of portions of at least two of the multiplereference pictures are different is satisfied. In some embodiments, afirst pairwise merge candidate is marked as unavailable in casedimensions of portions of at least two of the multiple referencepictures used to derive the first pairwise merge candidate for one ortwo reference picture lists are different. In some embodiments, thesyntax element indicating the usage of the coding tool is conditionallysignaled in the bitstream representation based on the dimensions of theportions. In some embodiments, the syntax element indicating the usageof the coding tool is omitted in the bitstream representation.

In some embodiments, the syntax element indicating the usage of thecoding tool is conditionally included in the bitstream representationfurther based on whether a reference picture resampling (RPR) process isenabled. In some embodiments, the syntax element comprising one ofamvr_precision_idx, sym_mvd_flag, or mmvd_merge_flag. In someembodiments, the conversion according to the usage of the coding tool ismodified based on the dimensions of the portions. In some embodiments,the conversion comprises deriving a motion vector difference for areference picture list in a symmetric motion vector difference process,the deriving is based on a difference of dimensions of portions of atleast two of the multiple reference pictures. In some embodiments, theconversion comprises deriving a pairwise merge candidate, and thederiving comprises applying a weighted average based on a difference ofdimensions of portions of at least two of the multiple referencepictures.

FIG. 14 is a flowchart representation of a method 1400 of videoprocessing in accordance with the present technology. The method 1400includes, at operation 1410, performing a conversion between a block ofa video and a bitstream representation of the video. During theconversion an adaptive motion vector resolution (AMVR) with 1/2-pelmotion vector precision is enabled for the block due to a referencepicture resampling process is applicable to the block.

In some embodiments, a different interpolation filter is used for blockshaving a precision different than 1/2-pel precision. In someembodiments, the condition associated with the dimension of the portionof the reference picture is indicated by a flag associated with thereference picture. In some embodiments, the coding tool is disabled incase the flag indicates that at least one reference picture in areference picture list is scaled. In some embodiments, the flagcomprises RefPicIsScaled[0][refIdxL0], wherein refIdxL0 is an index fora first reference picture list. In some embodiments, the flag comprisesRefPicIsScaled[0][refIdxL1], wherein refIdxL1 is an index for secondfirst reference picture list. In some embodiments, the flag isdetermined during a reference picture list construction process.

FIG. 15 is a flowchart representation of a method 1500 of videoprocessing in accordance with the present technology. The method 1500includes, at operation 1510, determining, for a conversion between ablock of a video and a bitstream representation of the video, a sum ofabsolution difference used in a Bi-Directional Optical Flow (BDOF)coding tool or a Decoder-side Motion Vector Refinement (DMVR) codingtool in a manner that is based on a bit-depth of the block. The method1500 also includes, at operation 1520, performing the conversion basedon the determining.

In some embodiments, the sum of absolution difference is shifted basedon a function of the bit-depth before being compared to a threshold forthe BDOF coding tool or the DMVR coding tool. In some embodiments, thesum of absolution difference is compared to a threshold that is modifiedbased on a function of the bit-depth.

In some embodiments, the conversion includes encoding the video into thebitstream representation. In some embodiments, the conversion includesdecoding the bitstream representation into the video.

Some embodiments of the disclosed technology include making a decisionor determination to enable a video processing tool or mode. In anexample, when the video processing tool or mode is enabled, the encoderwill use or implement the tool or mode in the processing of a block ofvideo, but may not necessarily modify the resulting bitstream based onthe usage of the tool or mode. That is, a conversion from the block ofvideo to the bitstream representation of the video will use the videoprocessing tool or mode when it is enabled based on the decision ordetermination. In another example, when the video processing tool ormode is enabled, the decoder will process the bitstream with theknowledge that the bitstream has been modified based on the videoprocessing tool or mode. That is, a conversion from the bitstreamrepresentation of the video to the block of video will be performedusing the video processing tool or mode that was enabled based on thedecision or determination.

Some embodiments of the disclosed technology include making a decisionor determination to disable a video processing tool or mode. In anexample, when the video processing tool or mode is disabled, the encoderwill not use the tool or mode in the conversion of the block of video tothe bitstream representation of the video. In another example, when thevideo processing tool or mode is disabled, the decoder will process thebitstream with the knowledge that the bitstream has not been modifiedusing the video processing tool or mode that was enabled based on thedecision or determination.

The disclosed and other solutions, examples, embodiments, modules andthe functional operations described in this document can be implementedin digital electronic circuitry, or in computer software, firmware, orhardware, including the structures disclosed in this document and theirstructural equivalents, or in combinations of one or more of them. Thedisclosed and other embodiments can be implemented as one or morecomputer program products, e.g., one or more modules of computer programinstructions encoded on a computer readable medium for execution by, orto control the operation of, data processing apparatus. The computerreadable medium can be a machine-readable storage device, amachine-readable storage substrate, a memory device, a composition ofmatter effecting a machine-readable propagated signal, or a combinationof one or more them. The term “data processing apparatus” encompassesall apparatus, devices, and machines for processing data, including byway of example a programmable processor, a computer, or multipleprocessors or computers. The apparatus can include, in addition tohardware, code that creates an execution environment for the computerprogram in question, e.g., code that constitutes processor firmware, aprotocol stack, a database management system, an operating system, or acombination of one or more of them. A propagated signal is anartificially generated signal, e.g., a machine-generated electrical,optical, or electromagnetic signal, that is generated to encodeinformation for transmission to suitable receiver apparatus.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, and it can bedeployed in any form, including as a stand-alone program or as a module,component, subroutine, or other unit suitable for use in a computingenvironment. A computer program does not necessarily correspond to afile in a file system. A program can be stored in a portion of a filethat holds other programs or data (e.g., one or more scripts stored in amarkup language document), in a single file dedicated to the program inquestion, or in multiple coordinated files (e.g., files that store oneor more modules, sub programs, or portions of code). A computer programcan be deployed to be executed on one computer or on multiple computersthat are located at one site or distributed across multiple sites andinterconnected by a communication network.

The processes and logic flows described in this document can beperformed by one or more programmable processors executing one or morecomputer programs to perform functions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read only memory ora random-access memory or both. The essential elements of a computer area processor for performing instructions and one or more memory devicesfor storing instructions and data. Generally, a computer will alsoinclude, or be operatively coupled to receive data from or transfer datato, or both, one or more mass storage devices for storing data, e.g.,magnetic, magneto optical disks, or optical disks. However, a computerneed not have such devices. Computer readable media suitable for storingcomputer program instructions and data include all forms of non-volatilememory, media and memory devices, including by way of examplesemiconductor memory devices, e.g., EPROM, EEPROM, and flash memorydevices; magnetic disks, e.g., internal hard disks or removable disks;magneto optical disks; and CD ROM and DVD-ROM disks. The processor andthe memory can be supplemented by, or incorporated in, special purposelogic circuitry.

While this patent document contains many specifics, these should not beconstrued as limitations on the scope of any subject matter or of whatmay be claimed, but rather as descriptions of features that may bespecific to particular embodiments of particular techniques. Certainfeatures that are described in this patent document in the context ofseparate embodiments can also be implemented in combination in a singleembodiment. Conversely, various features that are described in thecontext of a single embodiment can also be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. Moreover, the separation of various system components in theembodiments described in this patent document should not be understoodas requiring such separation in all embodiments.

Only a few implementations and examples are described and otherimplementations, enhancements and variations can be made based on whatis described and illustrated in this patent document.

What is claimed is:
 1. A method of video processing, comprising:determining, for a conversion between a current block of a currentpicture of a video and a bitstream of the video, whether to disable acoding tool for the current block; and performing the conversion basedon the determining, wherein the coding tool is disabled when a dimensionof a reference picture of one or more reference pictures of the currentblock is different from a dimension of the current picture, or adimension of a scaling window in a reference picture of one or morereference pictures of the current block is different from a dimension ofa scaling window in the current picture.
 2. The method of claim 1,wherein the coding tool comprises a first refinement coding tool, andwherein the first refinement coding tool refines a signaled motionvector based on at least one motion vector with an offset to thesignaled motion vector.
 3. The method of claim 1, wherein the codingtool comprises a second refinement coding tool, and wherein the secondrefinement coding tool obtains a motion vector refinement based on atleast one gradient value corresponding to a sample in a reference blockof the current block.
 4. The method of claim 1, wherein an affine modeis applied to the current block and initial prediction samples of asub-block of the current block is generated, wherein the coding toolcomprises a third refinement coding tool, wherein the third refinementcoding tool is applied to generate final prediction samples for thesub-block by deriving a prediction refinement based on motion vectordifferences dMvH and/or dMvV, and wherein dMvH and dMvV indicate motionvector differences along a horizontal direction and a verticaldirection.
 5. The method of claim 4, wherein the third refinement codingtool is disabled for a first reference picture list of the current blockwhen a dimension of a reference picture in the first reference picturelist is different from a dimension of the current picture, or adimension of a scaling window in a reference picture in the firstreference picture list is different from a dimension of a scaling windowin the current picture, and wherein the third refinement coding tool isdisabled for a second reference picture list of the current block when adimension of a reference picture in the second reference picture list isdifferent from a dimension of the current picture, or a dimension of ascaling window in a reference picture in the second reference picturelist is different from a dimension of a scaling window in the currentpicture.
 6. The method of claim 1, wherein whether the coding tool isdisabled is determined based on values of one or more constraint activeflags associated with the one or more reference pictures respectively.7. The method of claim 6, wherein when a dimension of a referencepicture in a first reference picture list of the current block isdifferent from a dimension of the current picture, or a dimension of ascaling window in a reference picture in a first reference picture listof the current block is different from a dimension of a scaling windowin the current picture, a value of a first constraint active flag is setto be unequal to 0, and when a dimension of a reference picture in asecond reference picture list of the current block is different from adimension of the current picture, or a dimension of a scaling window ina reference picture in a second reference picture list of the currentblock is different from a dimension of a scaling window in the currentpicture, a value of a second constraint active flag is set to be unequalto
 0. 8. The method of claim 6, wherein the one or more constraintactive flags are derived during a reference picture list constructionprocess.
 9. The method of claim 1, wherein a dimension of a scalingwindow is determined based on at least one of 1)scaling_win_left_offset, 2) scaling_win_right_offset, 3)scaling_win_bottom_offset, or 4) scaling_win_top_offset.
 10. The methodof claim 1, wherein an adaptive motion vector resolution is enabled forthe current block when a dimension of a reference picture of one or morereference pictures of the current block is different from a dimension ofthe current picture, or a dimension of a scaling window in a referencepicture of one or more reference pictures of the current block isdifferent from a dimension of a scaling window in the current picture.11. The method of claim 1, wherein the conversion includes encoding thecurrent picture into the bitstream.
 12. The method of claim 1, whereinthe conversion includes decoding the current picture from the bitstream.13. An apparatus for processing video data comprising a processor and anon-transitory memory with instructions thereon, wherein theinstructions upon execution by the processor, cause the processor to:determine, for a conversion between a current block of a current pictureof a video and a bitstream of the video, whether to disable a codingtool for the current block; and perform the conversion based on thedetermining, wherein the coding tool is disabled when a dimension of areference picture of one or more reference pictures of the current blockis different from a dimension of the current picture, or a dimension ofa scaling window in a reference picture of one or more referencepictures of the current block is different from a dimension of a scalingwindow in the current picture.
 14. The apparatus of claim 13, whereinthe coding tool comprises a first refinement coding tool, and whereinthe first refinement coding tool refines a signaled motion vector basedon at least one motion vector with an offset to the signaled motionvector.
 15. The apparatus of claim 13, wherein the coding tool comprisesa second refinement coding tool, and wherein the second refinementcoding tool obtains a motion vector refinement based on at least onegradient value corresponding to a sample in a reference block of thecurrent block.
 16. The apparatus of claim 13, wherein an affine mode isapplied to the current block and initial prediction samples of asub-block of the current block is generated, wherein the coding toolcomprises a third refinement coding tool, wherein the third refinementcoding tool is applied to generate final prediction samples for thesub-block by deriving a prediction refinement based on motion vectordifferences dMvH and/or dMvV, and wherein dMvH and dMvV indicate motionvector differences along a horizontal direction and a verticaldirection.
 17. The apparatus of claim 16, wherein the third refinementcoding tool is disabled for a first reference picture list of thecurrent block when a dimension of a reference picture in the firstreference picture list is different from a dimension of the currentpicture, or a dimension of a scaling window in a reference picture inthe first reference picture list is different from a dimension of ascaling window in the current picture, and wherein the third refinementcoding tool is disabled for a second reference picture list of thecurrent block when a dimension of a reference picture in the secondreference picture list is different from a dimension of the currentpicture, or a dimension of a scaling window in a reference picture inthe second reference picture list is different from a dimension of ascaling window in the current picture.
 18. The apparatus of claim 13,wherein whether the coding tool is disabled is determined based onvalues of one or more constraint active flags associated with the one ormore reference pictures respectively.
 19. A non-transitorycomputer-readable storage medium storing instructions that cause aprocessor to: determine, for a conversion between a current block of acurrent picture of a video and a bitstream of the video, whether todisable a coding tool for the current block; and perform the conversionbased on the determining, wherein the coding tool is disabled when adimension of a reference picture of one or more reference pictures ofthe current block is different from a dimension of the current picture,or a dimension of a scaling window in a reference picture of one or morereference pictures of the current block is different from a dimension ofa scaling window in the current picture.
 20. A non-transitorycomputer-readable recording medium storing a bitstream of a video whichis generated by a method performed by a video processing apparatus,wherein the method comprises: determining, for a current block of acurrent picture of a video, whether to disable a coding tool for thecurrent block; and generating the bitstream based on the determining,wherein the coding tool is disabled when a dimension of a referencepicture of one or more reference pictures of the current block isdifferent from a dimension of the current picture, or a dimension of ascaling window in a reference picture of one or more reference picturesof the current block is different from a dimension of a scaling windowin the current picture.